/IronPython_Main/Languages/IronPython/IronPython/Runtime/Operations/PythonOps.cs

/* ****************************************************************************

 *

 * Copyright (c) Microsoft Corporation. 

 *

 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 

 * copy of the license can be found in the License.html file at the root of this distribution. If 

 * you cannot locate the  Apache License, Version 2.0, please send an email to 

 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 

 * by the terms of the Apache License, Version 2.0.

 *

 * You must not remove this notice, or any other, from this software.

 *

 *

 * ***************************************************************************/



#if !CLR2

using System.Linq.Expressions;

using System.Numerics;

using Microsoft.Scripting.Ast;

#else

using Microsoft.Scripting.Ast;

using Microsoft.Scripting.Math;

using Complex = Microsoft.Scripting.Math.Complex64;

#endif



using System;

using System.Collections;

using System.Collections.Generic;

using System.Diagnostics;

using System.Dynamic;

using System.IO;

using System.Reflection;

using System.Reflection.Emit;

using System.Runtime.CompilerServices;

using System.Runtime.InteropServices;

using System.Text;

using System.Threading;



using Microsoft.Scripting;

using Microsoft.Scripting.Actions;

using Microsoft.Scripting.Generation;

using Microsoft.Scripting.Hosting.Providers;

using Microsoft.Scripting.Hosting.Shell;

using Microsoft.Scripting.Runtime;

using Microsoft.Scripting.Utils;



using IronPython.Compiler;

using IronPython.Hosting;

using IronPython.Modules;

using IronPython.Runtime.Binding;

using IronPython.Runtime.Exceptions;

using IronPython.Runtime.Types;



#if !SILVERLIGHT

using System.ComponentModel;

#endif



namespace IronPython.Runtime.Operations {



    /// <summary>

    /// Contains functions that are called directly from

    /// generated code to perform low-level runtime functionality.

    /// </summary>

    public static partial class PythonOps {

        #region Shared static data



        [ThreadStatic]

        private static List<object> InfiniteRepr;



        // The "current" exception on this thread that will be returned via sys.exc_info()

        [ThreadStatic]

        internal static Exception RawException;



        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes")]

        public static readonly PythonTuple EmptyTuple = PythonTuple.EMPTY;

        private static readonly Type[] _DelegateCtorSignature = new Type[] { typeof(object), typeof(IntPtr) };



        #endregion



        public static BigInteger MakeIntegerFromHex(string s) {

            return LiteralParser.ParseBigInteger(s, 16);

        }



        public static PythonDictionary MakeDict(int size) {

            return new PythonDictionary(size);

        }



        public static PythonDictionary MakeEmptyDict() {

            return new PythonDictionary(EmptyDictionaryStorage.Instance);

        }



        /// <summary>

        /// Creates a new dictionary extracting the keys and values from the

        /// provided data array.  Keys/values are adjacent in the array with

        /// the value coming first.

        /// </summary>

        public static PythonDictionary MakeDictFromItems(params object[] data) {

            return new PythonDictionary(new CommonDictionaryStorage(data, false));

        }



        public static PythonDictionary MakeConstantDict(object items) {

            return new PythonDictionary((ConstantDictionaryStorage)items);

        }



        public static object MakeConstantDictStorage(params object[] data) {

            return new ConstantDictionaryStorage(new CommonDictionaryStorage(data, false));

        }



        public static SetCollection MakeSet(params object[] items) {

            return new SetCollection(items);

        }



        public static SetCollection MakeEmptySet() {

            return new SetCollection();

        }



        /// <summary>

        /// Creates a new dictionary extracting the keys and values from the

        /// provided data array.  Keys/values are adjacent in the array with

        /// the value coming first.

        /// </summary>

        public static PythonDictionary MakeHomogeneousDictFromItems(object[] data) {

            return new PythonDictionary(new CommonDictionaryStorage(data, true));

        }



        public static bool IsCallable(CodeContext/*!*/ context, object o) {

            // This tells if an object can be called, but does not make a claim about the parameter list.

            // In 1.x, we could check for certain interfaces like ICallable*, but those interfaces were deprecated

            // in favor of dynamic sites. 

            // This is difficult to infer because we'd need to simulate the entire callbinder, which can include

            // looking for [SpecialName] call methods and checking for a rule from IDynamicMetaObjectProvider. But even that wouldn't

            // be complete since sites require the argument list of the call, and we only have the instance here. 

            // Thus check a dedicated IsCallable operator. This lets each object describe if it's callable.





            // Invoke Operator.IsCallable on the object. 

            return PythonContext.GetContext(context).IsCallable(o);

        }



        public static bool UserObjectIsCallable(CodeContext/*!*/ context, object o) {

            object callFunc;

            return TryGetBoundAttr(context, o, "__call__", out callFunc) && callFunc != null;

        }



        public static bool IsTrue(object o) {

            return Converter.ConvertToBoolean(o);

        }



        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1002:DoNotExposeGenericLists")]

        public static List<object> GetReprInfinite() {

            if (InfiniteRepr == null) {

                InfiniteRepr = new List<object>();

            }

            return InfiniteRepr;

        }



        [LightThrowing]

        internal static object LookupEncodingError(CodeContext/*!*/ context, string name) {

            Dictionary<string, object> errorHandlers = PythonContext.GetContext(context).ErrorHandlers;

            lock (errorHandlers) {

                if (errorHandlers.ContainsKey(name))

                    return errorHandlers[name];

                else

                    return LightExceptions.Throw(PythonOps.LookupError("unknown error handler name '{0}'", name));

            }

        }



        internal static void RegisterEncodingError(CodeContext/*!*/ context, string name, object handler) {

            Dictionary<string, object> errorHandlers = PythonContext.GetContext(context).ErrorHandlers;



            lock (errorHandlers) {

                if (!PythonOps.IsCallable(context, handler))

                    throw PythonOps.TypeError("handler must be callable");



                errorHandlers[name] = handler;

            }

        }



        internal static PythonTuple LookupEncoding(CodeContext/*!*/ context, string encoding) {

            PythonContext.GetContext(context).EnsureEncodings();



            List<object> searchFunctions = PythonContext.GetContext(context).SearchFunctions;

            string normalized = encoding.ToLower().Replace(' ', '-');

            if (normalized.IndexOf(Char.MinValue) != -1) {

                throw PythonOps.TypeError("lookup string cannot contain null character");

            }

            lock (searchFunctions) {

                for (int i = 0; i < searchFunctions.Count; i++) {

                    object res = PythonCalls.Call(context, searchFunctions[i], normalized);

                    if (res != null) return (PythonTuple)res;

                }

            }



            throw PythonOps.LookupError("unknown encoding: {0}", encoding);

        }



        internal static void RegisterEncoding(CodeContext/*!*/ context, object search_function) {

            if (!PythonOps.IsCallable(context, search_function))

                throw PythonOps.TypeError("search_function must be callable");



            List<object> searchFunctions = PythonContext.GetContext(context).SearchFunctions;



            lock (searchFunctions) {

                searchFunctions.Add(search_function);

            }

        }



        internal static string GetPythonTypeName(object obj) {

            OldInstance oi = obj as OldInstance;

            if (oi != null) return oi._class._name.ToString();

            else return PythonTypeOps.GetName(obj);

        }



        public static string Repr(CodeContext/*!*/ context, object o) {

            if (o == null) return "None";



            string s;

            if ((s = o as string) != null) return StringOps.__repr__(s);

            if (o is int) return Int32Ops.__repr__((int)o);

            if (o is long) return ((long)o).ToString() + "L";



            // could be a container object, we need to detect recursion, but only

            // for our own built-in types that we're aware of.  The user can setup

            // infinite recursion in their own class if they want.

            ICodeFormattable f = o as ICodeFormattable;

            if (f != null) {

                return f.__repr__(context);

            }



            PerfTrack.NoteEvent(PerfTrack.Categories.Temporary, "Repr " + o.GetType().FullName);



            return PythonContext.InvokeUnaryOperator(context, UnaryOperators.Repr, o) as string;

        }



        public static List<object> GetAndCheckInfinite(object o) {

            List<object> infinite = GetReprInfinite();

            foreach (object o2 in infinite) {

                if (o == o2) {

                    return null;

                }

            }

            return infinite;

        }



        public static string ToString(object o) {

            return ToString(DefaultContext.Default, o);

        }



        public static string ToString(CodeContext/*!*/ context, object o) {

            string x = o as string;

            PythonType dt;

            OldClass oc;

            if (x != null) return x;

            if (o == null) return "None";

            if (o is double) return DoubleOps.__str__(context, (double)o);

            if ((dt = o as PythonType) != null) return dt.__repr__(DefaultContext.Default);

            if ((oc = o as OldClass) != null) return oc.ToString();



            object value = PythonContext.InvokeUnaryOperator(context, UnaryOperators.String, o);

            string ret = value as string;

            if (ret == null) {

                Extensible<string> es = value as Extensible<string>;

                if (es == null) {

                    throw PythonOps.TypeError("expected str, got {0} from __str__", PythonTypeOps.GetName(value));

                }



                ret = es.Value;

            }

            

            return ret;

        }



        public static string FormatString(CodeContext/*!*/ context, string str, object data) {

            return new StringFormatter(context, str, data).Format();

        }



        public static string FormatUnicode(CodeContext/*!*/ context, string str, object data) {

            return new StringFormatter(context, str, data, true).Format();

        }



        public static object Plus(object o) {

            object ret;



            if (o is int) return o;

            else if (o is double) return o;

            else if (o is BigInteger) return o;

            else if (o is Complex) return o;

            else if (o is long) return o;

            else if (o is float) return o;

            else if (o is bool) return ScriptingRuntimeHelpers.Int32ToObject((bool)o ? 1 : 0);



            if (PythonTypeOps.TryInvokeUnaryOperator(DefaultContext.Default, o, "__pos__", out ret) &&

                ret != NotImplementedType.Value) {

                return ret;

            }



            throw PythonOps.TypeError("bad operand type for unary +");

        }



        public static object Negate(object o) {

            if (o is int) return Int32Ops.Negate((int)o);

            else if (o is double) return DoubleOps.Negate((double)o);

            else if (o is long) return Int64Ops.Negate((long)o);

            else if (o is BigInteger) return BigIntegerOps.Negate((BigInteger)o);

            else if (o is Complex) return -(Complex)o;

            else if (o is float) return DoubleOps.Negate((float)o);

            else if (o is bool) return ScriptingRuntimeHelpers.Int32ToObject((bool)o ? -1 : 0);



            object ret;

            if (PythonTypeOps.TryInvokeUnaryOperator(DefaultContext.Default, o, "__neg__", out ret) &&

                ret != NotImplementedType.Value) {

                return ret;

            }



            throw PythonOps.TypeError("bad operand type for unary -");

        }



        public static bool IsSubClass(PythonType/*!*/ c, PythonType/*!*/ typeinfo) {

            Assert.NotNull(c, typeinfo);



            if (c.OldClass != null) {

                return typeinfo.__subclasscheck__(c.OldClass);

            }



            return typeinfo.__subclasscheck__(c);

        }



        public static bool IsSubClass(CodeContext/*!*/ context, PythonType c, object typeinfo) {

            if (c == null) throw PythonOps.TypeError("issubclass: arg 1 must be a class");

            if (typeinfo == null) throw PythonOps.TypeError("issubclass: arg 2 must be a class");



            PythonTuple pt = typeinfo as PythonTuple;

            PythonContext pyContext = PythonContext.GetContext(context);

            if (pt != null) {

                // Recursively inspect nested tuple(s)

                foreach (object o in pt) {

                    try {

                        FunctionPushFrame(pyContext);

                        if (IsSubClass(context, c, o)) {

                            return true;

                        }

                    } finally {

                        FunctionPopFrame();

                    }

                }

                return false;

            }



            OldClass oc = typeinfo as OldClass;

            if (oc != null) {

                return c.IsSubclassOf(oc.TypeObject);

            }



            Type t = typeinfo as Type;

            if (t != null) {

                typeinfo = DynamicHelpers.GetPythonTypeFromType(t);

            }



            object bases;

            PythonType dt = typeinfo as PythonType;

            if (dt == null) {

                if (!PythonOps.TryGetBoundAttr(typeinfo, "__bases__", out bases)) {

                    //!!! deal with classes w/ just __bases__ defined.

                    throw PythonOps.TypeErrorForBadInstance("issubclass(): {0} is not a class nor a tuple of classes", typeinfo);

                }



                IEnumerator ie = PythonOps.GetEnumerator(bases);

                while (ie.MoveNext()) {

                    PythonType baseType = ie.Current as PythonType;



                    if (baseType == null) {

                        OldClass ocType = ie.Current as OldClass;

                        if (ocType == null) {

                            continue;

                        }



                        baseType = ocType.TypeObject;

                    }



                    if (c.IsSubclassOf(baseType)) return true;

                }

                return false;

            }



            return IsSubClass(c, dt);

        }



        public static bool IsInstance(object o, PythonType typeinfo) {

            if (typeinfo.__instancecheck__(o)) {

                return true;

            }



            return IsInstanceDynamic(o, typeinfo, DynamicHelpers.GetPythonType(o));

        }



        public static bool IsInstance(CodeContext/*!*/ context, object o, PythonTuple typeinfo) {

            PythonContext pyContext = PythonContext.GetContext(context);

            foreach (object type in typeinfo) {

                try {

                    PythonOps.FunctionPushFrame(pyContext);

                    if (type is PythonType) {

                        if (IsInstance(o, (PythonType)type)) {

                            return true;

                        }

                    } else if (type is PythonTuple) {

                        if (IsInstance(context, o, (PythonTuple)type)) {

                            return true;

                        }

                    } else if (IsInstance(context, o, type)) {

                        return true;

                    }

                } finally {

                    PythonOps.FunctionPopFrame();

                }

            }

            return false;

        }



        public static bool IsInstance(CodeContext/*!*/ context, object o, object typeinfo) {

            if (typeinfo == null) throw PythonOps.TypeError("isinstance: arg 2 must be a class, type, or tuple of classes and types");



            PythonTuple tt = typeinfo as PythonTuple;

            if (tt != null) {

                return IsInstance(context, o, tt);

            }



            if (typeinfo is OldClass) {

                // old instances are strange - they all share a common type

                // of instance but they can "be subclasses" of other

                // OldClass's.  To check their types we need the actual

                // instance.

                OldInstance oi = o as OldInstance;

                if (oi != null) return oi._class.IsSubclassOf(typeinfo);

            }



            PythonType odt = DynamicHelpers.GetPythonType(o);

            if (IsSubClass(context, odt, typeinfo)) {

                return true;

            }



            return IsInstanceDynamic(o, typeinfo);

        }



        private static bool IsInstanceDynamic(object o, object typeinfo) {

            return IsInstanceDynamic(o, typeinfo, DynamicHelpers.GetPythonType(o));

        }



        private static bool IsInstanceDynamic(object o, object typeinfo, PythonType odt) {

            if (o is IPythonObject || o is OldInstance) {

                object cls;

                if (PythonOps.TryGetBoundAttr(o, "__class__", out cls) &&

                    (!object.ReferenceEquals(odt, cls))) {

                    return IsSubclassSlow(cls, typeinfo);

                }

            }

            return false;

        }



        private static bool IsSubclassSlow(object cls, object typeinfo) {

            Debug.Assert(typeinfo != null);

            if (cls == null) return false;



            // Same type

            if (cls.Equals(typeinfo)) {

                return true;

            }



            // Get bases

            object bases;

            if (!PythonOps.TryGetBoundAttr(cls, "__bases__", out bases)) {

                return false;   // no bases, cannot be subclass

            }

            PythonTuple tbases = bases as PythonTuple;

            if (tbases == null) {

                return false;   // not a tuple, cannot be subclass

            }



            foreach (object baseclass in tbases) {

                if (IsSubclassSlow(baseclass, typeinfo)) return true;

            }



            return false;

        }



        public static object OnesComplement(object o) {

            if (o is int) return ~(int)o;

            if (o is long) return ~(long)o;

            if (o is BigInteger) return ~((BigInteger)o);

            if (o is bool) return ScriptingRuntimeHelpers.Int32ToObject((bool)o ? -2 : -1);



            object ret;

            if (PythonTypeOps.TryInvokeUnaryOperator(DefaultContext.Default, o, "__invert__", out ret) &&

                ret != NotImplementedType.Value)

                return ret;





            throw PythonOps.TypeError("bad operand type for unary ~");

        }



        public static bool Not(object o) {

            return !IsTrue(o);

        }



        public static object Is(object x, object y) {

            return x == y ? ScriptingRuntimeHelpers.True : ScriptingRuntimeHelpers.False;

        }



        public static bool IsRetBool(object x, object y) {

            return x == y;

        }



        public static object IsNot(object x, object y) {

            return x != y ? ScriptingRuntimeHelpers.True : ScriptingRuntimeHelpers.False;

        }



        public static bool IsNotRetBool(object x, object y) {

            return x != y;

        }



        internal delegate T MultiplySequenceWorker<T>(T self, int count);



        /// <summary>

        /// Wraps up all the semantics of multiplying sequences so that all of our sequences

        /// don't duplicate the same logic.  When multiplying sequences we need to deal with

        /// only multiplying by valid sequence types (ints, not floats), support coercion

        /// to integers if the type supports it, not multiplying by None, and getting the

        /// right semantics for multiplying by negative numbers and 1 (w/ and w/o subclasses).

        /// 

        /// This function assumes that it is only called for case where count is not implicitly

        /// coercible to int so that check is skipped.

        /// </summary>

        internal static object MultiplySequence<T>(MultiplySequenceWorker<T> multiplier, T sequence, Index count, bool isForward) {

            if (isForward && count != null) {

                object ret;

                if (PythonTypeOps.TryInvokeBinaryOperator(DefaultContext.Default, count.Value, sequence, "__rmul__", out ret)) {

                    if (ret != NotImplementedType.Value) return ret;

                }

            }



            int icount = GetSequenceMultiplier(sequence, count.Value);



            if (icount < 0) icount = 0;

            return multiplier(sequence, icount);

        }



        internal static int GetSequenceMultiplier(object sequence, object count) {

            int icount;

            if (!Converter.TryConvertToIndex(count, out icount)) {

                PythonTuple pt = null;

                if (count is OldInstance || !DynamicHelpers.GetPythonType(count).IsSystemType) {

                    pt = Builtin.TryCoerce(DefaultContext.Default, count, sequence) as PythonTuple;

                }



                if (pt == null || !Converter.TryConvertToIndex(pt[0], out icount)) {

                    throw TypeError("can't multiply sequence by non-int of type '{0}'", PythonTypeOps.GetName(count));

                }

            }

            return icount;

        }



        public static object Equal(CodeContext/*!*/ context, object x, object y) {

            PythonContext pc = PythonContext.GetContext(context);

            return pc.EqualSite.Target(pc.EqualSite, x, y);

        }



        public static bool EqualRetBool(object x, object y) {

            //TODO just can't seem to shake these fast paths

            if (x is int && y is int) { return ((int)x) == ((int)y); }

            if (x is string && y is string) { return ((string)x).Equals((string)y); }

            

            return DynamicHelpers.GetPythonType(x).EqualRetBool(x, y);

        }



        public static bool EqualRetBool(CodeContext/*!*/ context, object x, object y) {

            // TODO: use context



            //TODO just can't seem to shake these fast paths

            if (x is int && y is int) { return ((int)x) == ((int)y); }

            if (x is string && y is string) { return ((string)x).Equals((string)y); }



            return DynamicHelpers.GetPythonType(x).EqualRetBool(x, y);

        }



        public static int Compare(object x, object y) {

            return Compare(DefaultContext.Default, x, y);

        }



        public static int Compare(CodeContext/*!*/ context, object x, object y) {

            if (x == y) return 0;



            return DynamicHelpers.GetPythonType(x).Compare(x, y);

        }



        public static object CompareEqual(int res) {

            return res == 0 ? ScriptingRuntimeHelpers.True : ScriptingRuntimeHelpers.False;

        }



        public static object CompareNotEqual(int res) {

            return res == 0 ? ScriptingRuntimeHelpers.False : ScriptingRuntimeHelpers.True;

        }



        public static object CompareGreaterThan(int res) {

            return res > 0 ? ScriptingRuntimeHelpers.True : ScriptingRuntimeHelpers.False;

        }



        public static object CompareGreaterThanOrEqual(int res) {

            return res >= 0 ? ScriptingRuntimeHelpers.True : ScriptingRuntimeHelpers.False;

        }



        public static object CompareLessThan(int res) {

            return res < 0 ? ScriptingRuntimeHelpers.True : ScriptingRuntimeHelpers.False;

        }



        public static object CompareLessThanOrEqual(int res) {

            return res <= 0 ? ScriptingRuntimeHelpers.True : ScriptingRuntimeHelpers.False;

        }



        public static bool CompareTypesEqual(CodeContext/*!*/ context, object x, object y) {

            if (x == null && y == null) return true;

            if (x == null) return false;

            if (y == null) return false;



            if (DynamicHelpers.GetPythonType(x) == DynamicHelpers.GetPythonType(y)) {

                // avoid going to the ID dispenser if we have the same types...

                return x == y;

            }



            return PythonOps.CompareTypesWorker(context, false, x, y) == 0;

        }



        public static bool CompareTypesNotEqual(CodeContext/*!*/ context, object x, object y) {

            return PythonOps.CompareTypesWorker(context, false, x, y) != 0;

        }



        public static bool CompareTypesGreaterThan(CodeContext/*!*/ context, object x, object y) {

            return PythonOps.CompareTypes(context, x, y) > 0;

        }



        public static bool CompareTypesLessThan(CodeContext/*!*/ context, object x, object y) {

            return PythonOps.CompareTypes(context, x, y) < 0;

        }



        public static bool CompareTypesGreaterThanOrEqual(CodeContext/*!*/ context, object x, object y) {

            return PythonOps.CompareTypes(context, x, y) >= 0;

        }



        public static bool CompareTypesLessThanOrEqual(CodeContext/*!*/ context, object x, object y) {

            return PythonOps.CompareTypes(context, x, y) <= 0;

        }



        public static int CompareTypesWorker(CodeContext/*!*/ context, bool shouldWarn, object x, object y) {

            if (x == null && y == null) return 0;

            if (x == null) return -1;

            if (y == null) return 1;



            string name1, name2;

            int diff;



            if (DynamicHelpers.GetPythonType(x) != DynamicHelpers.GetPythonType(y)) {

                if (shouldWarn && PythonContext.GetContext(context).PythonOptions.WarnPython30) {

                    PythonOps.Warn(context, PythonExceptions.DeprecationWarning, "comparing unequal types not supported in 3.x");

                }



                if (x.GetType() == typeof(OldInstance)) {

                    name1 = ((OldInstance)x)._class.Name;

                    if (y.GetType() == typeof(OldInstance)) {

                        name2 = ((OldInstance)y)._class.Name;

                    } else {

                        // old instances are always less than new-style classes

                        return -1;

                    }

                } else if (y.GetType() == typeof(OldInstance)) {

                    // old instances are always less than new-style classes

                    return 1;

                } else {

                    name1 = PythonTypeOps.GetName(x);

                    name2 = PythonTypeOps.GetName(y);

                }

                diff = String.CompareOrdinal(name1, name2);

                if (diff == 0) {

                    // if the types are different but have the same name compare based upon their types. 

                    diff = (int)(IdDispenser.GetId(DynamicHelpers.GetPythonType(x)) - IdDispenser.GetId(DynamicHelpers.GetPythonType(y)));

                }

            } else {

                diff = (int)(IdDispenser.GetId(x) - IdDispenser.GetId(y));

            }



            if (diff < 0) return -1;

            if (diff == 0) return 0;

            return 1;

        }



        public static int CompareTypes(CodeContext/*!*/ context, object x, object y) {

            return CompareTypesWorker(context, true, x, y);

        }



        public static object GreaterThanHelper(CodeContext/*!*/ context, object self, object other) {

            return InternalCompare(context, PythonOperationKind.GreaterThan, self, other);

        }



        public static object LessThanHelper(CodeContext/*!*/ context, object self, object other) {

            return InternalCompare(context, PythonOperationKind.LessThan, self, other);

        }



        public static object GreaterThanOrEqualHelper(CodeContext/*!*/ context, object self, object other) {

            return InternalCompare(context, PythonOperationKind.GreaterThanOrEqual, self, other);

        }



        public static object LessThanOrEqualHelper(CodeContext/*!*/ context, object self, object other) {

            return InternalCompare(context, PythonOperationKind.LessThanOrEqual, self, other);

        }



        internal static object InternalCompare(CodeContext/*!*/ context, PythonOperationKind op, object self, object other) {

            object ret;

            if (PythonTypeOps.TryInvokeBinaryOperator(context, self, other, Symbols.OperatorToSymbol(op), out ret))

                return ret;



            return NotImplementedType.Value;

        }



        public static int CompareToZero(object value) {

            double val;

            if (Converter.TryConvertToDouble(value, out val)) {

                if (val > 0) return 1;

                if (val < 0) return -1;

                return 0;

            }

            throw PythonOps.TypeErrorForBadInstance("an integer is required (got {0})", value);

        }



        public static int CompareArrays(object[] data0, int size0, object[] data1, int size1) {

            int size = Math.Min(size0, size1);

            for (int i = 0; i < size; i++) {

                int c = PythonOps.Compare(data0[i], data1[i]);

                if (c != 0) return c;

            }

            if (size0 == size1) return 0;

            return size0 > size1 ? +1 : -1;

        }



        public static int CompareArrays(object[] data0, int size0, object[] data1, int size1, IComparer comparer) {

            int size = Math.Min(size0, size1);

            for (int i = 0; i < size; i++) {

                int c = comparer.Compare(data0[i], data1[i]);

                if (c != 0) return c;

            }

            if (size0 == size1) return 0;

            return size0 > size1 ? +1 : -1;

        }



        public static bool ArraysEqual(object[] data0, int size0, object[] data1, int size1) {

            if (size0 != size1) {

                return false;

            }

            for (int i = 0; i < size0; i++) {

                if (data0[i] != null) {

                    if (!EqualRetBool(data0[i], data1[i])) {

                        return false;

                    }

                } else if (data1[i] != null) {

                    return false;

                }

            }

            return true;

        }



        public static bool ArraysEqual(object[] data0, int size0, object[] data1, int size1, IEqualityComparer comparer) {

            if (size0 != size1) {

                return false;

            }

            for (int i = 0; i < size0; i++) {

                if (data0[i] != null) {

                    if (!comparer.Equals(data0[i], data1[i])) {

                        return false;

                    }

                } else if (data1[i] != null) {

                    return false;

                }

            }

            return true;

        }



        public static object PowerMod(CodeContext/*!*/ context, object x, object y, object z) {

            object ret;

            if (z == null) {

                return PythonContext.GetContext(context).Operation(PythonOperationKind.Power, x, y);

            }

            if (x is int && y is int && z is int) {

                ret = Int32Ops.Power((int)x, (int)y, (int)z);

                if (ret != NotImplementedType.Value) return ret;

            } else if (x is BigInteger) {

                ret = BigIntegerOps.Power((BigInteger)x, y, z);

                if (ret != NotImplementedType.Value) return ret;

            }



            if (x is Complex || y is Complex || z is Complex) {

                throw PythonOps.ValueError("complex modulo");

            }



            if (PythonTypeOps.TryInvokeTernaryOperator(context, x, y, z, "__pow__", out ret)) {

                if (ret != NotImplementedType.Value) {

                    return ret;

                } else if (!IsNumericObject(y) || !IsNumericObject(z)) {

                    // special error message in this case...

                    throw TypeError("pow() 3rd argument not allowed unless all arguments are integers");

                }

            }



            throw PythonOps.TypeErrorForBinaryOp("power with modulus", x, y);

        }



        public static long Id(object o) {

            return IdDispenser.GetId(o);

        }



        public static string HexId(object o) {

            return string.Format("0x{0:X16}", Id(o));

        }



        // For hash operators, it's essential that:

        //  Cmp(x,y)==0 implies hash(x) == hash(y)

        //

        // Equality is a language semantic determined by the Python's numerical Compare() ops 

        // in IronPython.Runtime.Operations namespaces.

        // For example, the CLR compares float(1.0) and int32(1) as different, but Python

        // compares them as equal. So Hash(1.0f) and Hash(1) must be equal.

        //

        // Python allows an equality relationship between int, double, BigInteger, and complex.

        // So each of these hash functions must be aware of their possible equality relationships

        // and hash appropriately.

        //

        // Types which differ in hashing from .NET have __hash__ functions defined in their

        // ops classes which do the appropriate hashing.        

        public static int Hash(CodeContext/*!*/ context, object o) {

            return PythonContext.Hash(o);

        }



        public static object Hex(object o) {

            if (o is int) return Int32Ops.__hex__((int)o);

            else if (o is BigInteger) return BigIntegerOps.__hex__((BigInteger)o);



            object hex;

            if (PythonTypeOps.TryInvokeUnaryOperator(DefaultContext.Default,

                o,

                "__hex__",

                out hex)) {

                if (!(hex is string) && !(hex is ExtensibleString))

                    throw PythonOps.TypeError("hex expected string type as return, got '{0}'", PythonTypeOps.GetName(hex));



                return hex;

            }

            throw TypeError("hex() argument cannot be converted to hex");

        }



        public static object Oct(object o) {

            if (o is int) {

                return Int32Ops.__oct__((int)o);

            } else if (o is BigInteger) {

                return BigIntegerOps.__oct__((BigInteger)o);

            }



            object octal;



            if (PythonTypeOps.TryInvokeUnaryOperator(DefaultContext.Default,

                o,

                "__oct__",

                out octal)) {

                if (!(octal is string) && !(octal is ExtensibleString))

                    throw PythonOps.TypeError("hex expected string type as return, got '{0}'", PythonTypeOps.GetName(octal));



                return octal;

            }

            throw TypeError("oct() argument cannot be converted to octal");

        }



        public static int Length(object o) {

            string s = o as string;

            if (s != null) {

                return s.Length;

            }



            object[] os = o as object[];

            if (os != null) {

                return os.Length;

            }



            object len = PythonContext.InvokeUnaryOperator(DefaultContext.Default, UnaryOperators.Length, o, "len() of unsized object");



            int res;

            if (len is int) {

                res = (int)len;

            } else {

                res = Converter.ConvertToInt32(len);

            }



            if (res < 0) {

                throw PythonOps.ValueError("__len__ should return >= 0, got {0}", res);

            }

            return res;

        }



        public static object CallWithContext(CodeContext/*!*/ context, object func, params object[] args) {

            return PythonCalls.Call(context, func, args);

        }



        /// <summary>

        /// Supports calling of functions that require an explicit 'this'

        /// Currently, we check if the function object implements the interface 

        /// that supports calling with 'this'. If not, the 'this' object is dropped

        /// and a normal call is made.

        /// </summary>

        public static object CallWithContextAndThis(CodeContext/*!*/ context, object func, object instance, params object[] args) {

            // drop the 'this' and make the call

            return CallWithContext(context, func, args);

        }



        public static object ToPythonType(PythonType dt) {

            if (dt != null) {

                return ((object)dt.OldClass) ?? ((object)dt);

            }

            return null;

        }



        public static object CallWithArgsTupleAndContext(CodeContext/*!*/ context, object func, object[] args, object argsTuple) {

            PythonTuple tp = argsTuple as PythonTuple;

            if (tp != null) {

                object[] nargs = new object[args.Length + tp.__len__()];

                for (int i = 0; i < args.Length; i++) nargs[i] = args[i];

                for (int i = 0; i < tp.__len__(); i++) nargs[i + args.Length] = tp[i];

                return CallWithContext(context, func, nargs);

            }



            List allArgs = PythonOps.MakeEmptyList(args.Length + 10);

            allArgs.AddRange(args);

            IEnumerator e = PythonOps.GetEnumerator(argsTuple);

            while (e.MoveNext()) allArgs.AddNoLock(e.Current);



            return CallWithContext(context, func, allArgs.GetObjectArray());

        }



        [Obsolete("Use ObjectOpertaions instead")]

        public static object CallWithArgsTupleAndKeywordDictAndContext(CodeContext/*!*/ context, object func, object[] args, string[] names, object argsTuple, object kwDict) {

            IDictionary kws = kwDict as IDictionary;

            if (kws == null && kwDict != null) throw PythonOps.TypeError("argument after ** must be a dictionary");



            if ((kws == null || kws.Count == 0) && names.Length == 0) {

                List<object> largs = new List<object>(args);

                if (argsTuple != null) {

                    foreach (object arg in PythonOps.GetCollection(argsTuple))

                        largs.Add(arg);

                }

                return CallWithContext(context, func, largs.ToArray());

            } else {

                List<object> largs;



                if (argsTuple != null && args.Length == names.Length) {

                    PythonTuple tuple = argsTuple as PythonTuple;

                    if (tuple == null) tuple = new PythonTuple(argsTuple);



                    largs = new List<object>(tuple);

                    largs.AddRange(args);

                } else {

                    largs = new List<object>(args);

                    if (argsTuple != null) {

                        largs.InsertRange(args.Length - names.Length, PythonTuple.Make(argsTuple));

                    }

                }



                List<string> lnames = new List<string>(names);



                if (kws != null) {

                    IDictionaryEnumerator ide = kws.GetEnumerator();

                    while (ide.MoveNext()) {

                        lnames.Add((string)ide.Key);

                        largs.Add(ide.Value);

                    }

                }



                return PythonCalls.CallWithKeywordArgs(context, func, largs.ToArray(), lnames.ToArray());

            }

        }



        public static object CallWithKeywordArgs(CodeContext/*!*/ context, object func, object[] args, string[] names) {

            return PythonCalls.CallWithKeywordArgs(context, func, args, names);

        }



        public static object CallWithArgsTuple(object func, object[] args, object argsTuple) {

            PythonTuple tp = argsTuple as PythonTuple;

            if (tp != null) {

                object[] nargs = new object[args.Length + tp.__len__()];

                for (int i = 0; i < args.Length; i++) nargs[i] = args[i];

                for (int i = 0; i < tp.__len__(); i++) nargs[i + args.Length] = tp[i];

                return PythonCalls.Call(func, nargs);

            }



            List allArgs = PythonOps.MakeEmptyList(args.Length + 10);

            allArgs.AddRange(args);

            IEnumerator e = PythonOps.GetEnumerator(argsTuple);

            while (e.MoveNext()) allArgs.AddNoLock(e.Current);



            return PythonCalls.Call(func, allArgs.GetObjectArray());

        }



        public static object GetIndex(CodeContext/*!*/ context, object o, object index) {

            PythonContext pc = PythonContext.GetContext(context);

            return pc.GetIndexSite.Target(pc.GetIndexSite, o, index);

        }



        public static bool TryGetBoundAttr(object o, string name, out object ret) {

            return TryGetBoundAttr(DefaultContext.Default, o, name, out ret);

        }



        public static void SetAttr(CodeContext/*!*/ context, object o, string name, object value) {

            PythonContext.GetContext(context).SetAttr(context, o, name, value);

        }



        public static bool TryGetBoundAttr(CodeContext/*!*/ context, object o, string name, out object ret) {

            return DynamicHelpers.GetPythonType(o).TryGetBoundAttr(context, o, name, out ret);

        }



        public static void DeleteAttr(CodeContext/*!*/ context, object o, string name) {

            PythonContext.GetContext(context).DeleteAttr(context, o, name);

        }



        public static bool HasAttr(CodeContext/*!*/ context, object o, string name) {

            object dummy;

            try {

                return TryGetBoundAttr(context, o, name, out dummy);

            } catch (SystemExitException) {

                throw;

            } catch (KeyboardInterruptException) {

                // we don't catch ThreadAbortException because it will

                // automatically re-throw on it's own.

                throw;

            } catch {

                return false;

            }

        }



        public static object GetBoundAttr(CodeContext/*!*/ context, object o, string name) {

            object ret;

            if (!DynamicHelpers.GetPythonType(o).TryGetBoundAttr(context, o, name, out ret)) {

                if (o is OldClass) {

                    throw PythonOps.AttributeError("type object '{0}' has no attribute '{1}'",

                        ((OldClass)o).Name, name);

                } else {

                    throw PythonOps.AttributeError("'{0}' object has no attribute '{1}'", PythonTypeOps.GetName(o), name);

                }

            }



            return ret;

        }



        public static void ObjectSetAttribute(CodeContext/*!*/ context, object o, string name, object value) {

            if (!DynamicHelpers.GetPythonType(o).TrySetNonCustomMember(context, o, name, value))

                throw AttributeErrorForMissingOrReadonly(context, DynamicHelpers.GetPythonType(o), name);

        }



        public static void ObjectDeleteAttribute(CodeContext/*!*/ context, object o, string name) {

            if (!DynamicHelpers.GetPythonType(o).TryDeleteNonCustomMember(context, o, name)) {

                throw AttributeErrorForMissingOrReadonly(context, DynamicHelpers.GetPythonType(o), name);

            }

        }



        public static object ObjectGetAttribute(CodeContext/*!*/ context, object o, string name) {

            OldClass oc = o as OldClass;

            if (oc != null) {

                return oc.GetMember(context, name);

            }



            object value;

            if (DynamicHelpers.GetPythonType(o).TryGetNonCustomMember(context, o, name, out value)) {

                return value;

            }



            throw PythonOps.AttributeErrorForObjectMissingAttribute(o, name);

        }



        internal static IList<string> GetStringMemberList(IPythonMembersList pyMemList) {

            List<string> res = new List<string>();

            foreach (object o in pyMemList.GetMemberNames(DefaultContext.Default)) {

                if (o is string) {

                    res.Add((string)o);

                }

            }

            return res;

        }



        public static IList<object> GetAttrNames(CodeContext/*!*/ context, object o) {

            IPythonMembersList pyMemList = o as IPythonMembersList;

            if (pyMemList != null) {

                return pyMemList.GetMemberNames(context);

            }



            IMembersList memList = o as IMembersList;

            if (memList != null) {

                return new List(memList.GetMemberNames());

            }



            IPythonObject po = o as IPythonObject;

            if (po != null) {

                return po.PythonType.GetMemberNames(context, o);

            }



            List res = DynamicHelpers.GetPythonType(o).GetMemberNames(context, o);



#if !SILVERLIGHT



            if (o != null && Microsoft.Scripting.ComInterop.ComBinder.IsComObject(o)) {

                foreach (string name in Microsoft.Scripting.ComInterop.ComBinder.GetDynamicMemberNames(o)) {

                    if (!res.Contains(name)) {

                        res.AddNoLock(name);

                    }

                }

            }

#endif

            return res;

        }



        /// <summary>

        /// Called from generated code emitted by NewTypeMaker.

        /// </summary>

        public static void CheckInitializedAttribute(object o, object self, string name) {

            if (o == Uninitialized.Instance) {

                throw PythonOps.AttributeError("'{0}' object has no attribute '{1}'",

                    PythonTypeOps.GetName(self),

                    name);

            }

        }



        public static object GetUserSlotValue(CodeContext/*!*/ context, PythonTypeUserDescriptorSlot slot, object instance, PythonType type) {

            return slot.GetValue(context, instance, type);

        }



        /// <summary>

        /// Handles the descriptor protocol for user-defined objects that may implement __get__

        /// </summary>

        public static object GetUserDescriptor(object o, object instance, object context) {

            if (o is IPythonObject) {

                // slow, but only encountred for user defined descriptors.

                PerfTrack.NoteEvent(PerfTrack.Categories.DictInvoke, "__get__");

                object ret;

                if (PythonContext.TryInvokeTernaryOperator(DefaultContext.Default,

                    TernaryOperators.GetDescriptor,

                    o,

                    instance,

                    context,

                    out ret)) {

                    return ret;

                }

            }



            return o;

        }



        /// <summary>

        /// Handles the descriptor protocol for user-defined objects that may implement __set__

        /// </summary>

        public static bool TrySetUserDescriptor(object o, object instance, object value) {

            if (o != null && o.GetType() == typeof(OldInstance)) return false;   // only new-style classes have descriptors



            // slow, but only encountred for user defined descriptors.

            PerfTrack.NoteEvent(PerfTrack.Categories.DictInvoke, "__set__");



            object dummy;

            return PythonContext.TryInvokeTernaryOperator(DefaultContext.Default,

                TernaryOperators.SetDescriptor,

                o,

                instance,

                value,

                out dummy);

        }



        /// <summary>

        /// Handles the descriptor protocol for user-defined objects that may implement __delete__

        /// </summary>

        public static bool TryDeleteUserDescriptor(object o, object instance) {

            if (o != null && o.GetType() == typeof(OldInstance)) return false;   // only new-style classes can have descriptors



            // slow, but only encountred for user defined descriptors.

            PerfTrack.NoteEvent(PerfTrack.Categories.DictInvoke, "__delete__");



            object dummy;

            return PythonTypeOps.TryInvokeBinaryOperator(DefaultContext.Default,

                o,

                instance,

                "__delete__",

                out dummy);

        }



        public static object Invoke(CodeContext/*!*/ context, object target, string name, params object[] args) {

            return PythonCalls.Call(context, PythonOps.GetBoundAttr(context, target, name), args);

        }



        public static Delegate CreateDynamicDelegate(DynamicMethod meth, Type delegateType, object target) {

            // Always close delegate around its own instance of the frame

            return meth.CreateDelegate(delegateType, target);

        }



        public static double CheckMath(double v) {

            if (double.IsInfinity(v)) {

                throw PythonOps.OverflowError("math range error");

            } else if (double.IsNaN(v)) {

                throw PythonOps.ValueError("math domain error");

            } else {

                return v;

            }

        }



        public static double CheckMath(double input, double output) {

            if (double.IsInfinity(input) && double.IsInfinity(output) ||

                double.IsNaN(input) && double.IsNaN(output)) {

                return output;

            } else {

                return CheckMath(output);

            }

        }



        public static double CheckMath(double in0, double in1, double output) {

            if ((double.IsInfinity(in0) || double.IsInfinity(in1)) && double.IsInfinity(output) ||

                (double.IsNaN(in0) || double.IsNaN(in1)) && double.IsNaN(output)) {

                return output;

            } else {

                return CheckMath(output);

            }

        }



        public static object IsMappingType(CodeContext/*!*/ context, object o) {

            if (o is IDictionary || o is PythonDictionary || o is IDictionary<object, object> || o is PythonDictionary) {

                return ScriptingRuntimeHelpers.True;

            }

            object getitem;

            if ((o is IPythonObject || o is OldInstance) && PythonOps.TryGetBoundAttr(context, o, "__getitem__", out getitem)) {

                if (!PythonOps.IsClsVisible(context)) {

                    // in standard Python methods aren't mapping types, therefore

                    // if the user hasn't broken out of that box yet don't treat 

                    // them as mapping types.

                    if (o is BuiltinFunction) return ScriptingRuntimeHelpers.False;

                }

                return ScriptingRuntimeHelpers.True;

            }

            return ScriptingRuntimeHelpers.False;

        }



        public static int FixSliceIndex(int v, int len) {

            if (v < 0) v = len + v;

            if (v < 0) return 0;

            if (v > len) return len;

            return v;

        }



        public static long FixSliceIndex(long v, long len) {

            if (v < 0) v = len + v;

            if (v < 0) return 0;

            if (v > len) return len;

            return v;

        }



        public static void FixSlice(

            int length, object start, object stop, object step,

            out int ostart, out int ostop, out int ostep

        ) {

            if (step == null) {

                ostep = 1;

            } else {

                ostep = Converter.ConvertToIndex(step);

                if (ostep == 0) {

                    throw PythonOps.ValueError("step cannot be zero");

                }

            }



            if (start == null) {

                ostart = ostep > 0 ? 0 : length - 1;

            } else {

                ostart = Converter.ConvertToIndex(start);

                if (ostart < 0) {

                    ostart += length;

                    if (ostart < 0) {

                        ostart = ostep > 0 ? Math.Min(length, 0) : Math.Min(length - 1, -1);

                    }

                } else if (ostart >= length) {

                    ostart = ostep > 0 ? length : length - 1;

                }

            }



            if (stop == null) {

                ostop = ostep > 0 ? length : -1;

            } else {

                ostop = Converter.ConvertToIndex(stop);

                if (ostop < 0) {

                    ostop += length;

                    if (ostop < 0) {

                        ostop = ostep > 0 ? Math.Min(length, 0) : Math.Min(length - 1, -1);

                    }

                } else if (ostop >= length) {

                    ostop = ostep > 0 ? length : length - 1;

                }

            }

        }



        public static void FixSlice(

            long length, long? start, long? stop, long? step,

            out long ostart, out long ostop, out long ostep, out long ocount

        ) {

            if (step == null) {

                ostep = 1;

            } else if (step == 0) {

                throw PythonOps.ValueError("step cannot be zero");

            } else {

                ostep = step.Value;

            }



            if (start == null) {

                ostart = ostep > 0 ? 0 : length - 1;

            } else {

                ostart = start.Value;

                if (ostart < 0) {

                    ostart += length;

                    if (ostart < 0) {

                        ostart = ostep > 0 ? Math.Min(length, 0) : Math.Min(length - 1, -1);

                    }

                } else if (ostart >= length) {

                    ostart = ostep > 0 ? length : length - 1;

                }

            }



            if (stop == null) {

                ostop = ostep > 0 ? length : -1;

            } else {

                ostop = stop.Value;

                if (ostop < 0) {

                    ostop += length;

                    if (ostop < 0) {

                        ostop = ostep > 0 ? Math.Min(length, 0) : Math.Min(length - 1, -1);

                    }

                } else if (ostop >= length) {

                    ostop = ostep > 0 ? length : length - 1;

                }

            }



            ocount = Math.Max(0, ostep > 0 ? (ostop - ostart + ostep - 1) / ostep

                                           : (ostop - ostart + ostep + 1) / ostep);

        }



        public static int FixIndex(int v, int len) {

            if (v < 0) {

                v += len;

                if (v < 0) {

                    throw PythonOps.IndexError("index out of range: {0}", v - len);

                }

            } else if (v >= len) {

                throw PythonOps.IndexError("index out of range: {0}", v);

            }

            return v;

        }



        public static void InitializeForFinalization(CodeContext/*!*/ context, object newObject) {

            IWeakReferenceable iwr = newObject as IWeakReferenceable;

            Debug.Assert(iwr != null);



            InstanceFinalizer nif = new InstanceFinalizer(context, newObject);

            iwr.SetFinalizer(new WeakRefTracker(nif, nif));

        }



        private static object FindMetaclass(CodeContext/*!*/ context, PythonTuple bases, PythonDictionary dict) {

            // If dict['__metaclass__'] exists, it is used. 

            object ret;

            if (dict.TryGetValue("__metaclass__", out ret) && ret != null) return ret;



            // Otherwise, if there is at least one base class, its metaclass is used

            for (int i = 0; i < bases.__len__(); i++) {

                if (!(bases[i] is OldClass)) return DynamicHelpers.GetPythonType(bases[i]);

            }



            // Otherwise, if there's a global variable named __metaclass__, it is used.

            if (context.TryGetGlobalVariable("__metaclass__", out ret) && ret != null) {

                return ret;

            }



            //Otherwise, the classic metaclass (types.ClassType) is used.

            return TypeCache.OldInstance;

        }



        public static object MakeClass(FunctionCode funcCode, Func<CodeContext, CodeContext> body, CodeContext/*!*/ parentContext, string name, object[] bases, string selfNames) {

            Func<CodeContext, CodeContext> func = GetClassCode(parentContext, funcCode, body);



            return MakeClass(parentContext, name, bases, selfNames, func(parentContext).Dict);

        }



        private static Func<CodeContext, CodeContext> GetClassCode(CodeContext/*!*/ context, FunctionCode funcCode, Func<CodeContext, CodeContext> body) {

            if (body == null) {

                if (funcCode.Target == null) {

                    funcCode.UpdateDelegate(context.LanguageContext, true);

                }

                return (Func<CodeContext, CodeContext>)funcCode.Target;

            } else {

                if (funcCode.Target == null) {

                    funcCode.SetTarget(body);

                    funcCode._normalDelegate = body;

                }

                return body;

            }

        }



        internal static object MakeClass(CodeContext/*!*/ context, string name, object[] bases, string selfNames, PythonDictionary vars) {

            foreach (object dt in bases) {

                if (dt is TypeGroup) {

                    object[] newBases = new object[bases.Length];

                    for (int i = 0; i < bases.Length; i++) {

                        TypeGroup tc = bases[i] as TypeGroup;

                        if (tc != null) {

                            Type nonGenericType;

                            if (!tc.TryGetNonGenericType(out nonGenericType)) {

                                throw PythonOps.TypeError("cannot derive from open generic types " + Builtin.repr(context, tc).ToString());

                            }

                            newBases[i] = DynamicHelpers.GetPythonTypeFromType(nonGenericType);

                        } else {

                            newBases[i] = bases[i];

                        }

                    }

                    bases = newBases;

                    break;

                }

            }

            PythonTuple tupleBases = PythonTuple.MakeTuple(bases);



            object metaclass = FindMetaclass(context, tupleBases, vars);

            if (metaclass == TypeCache.OldInstance) {

                return new OldClass(name, tupleBases, vars, selfNames);

            } else if (metaclass == TypeCache.PythonType) {

                return PythonType.__new__(context, TypeCache.PythonType, name, tupleBases, vars, selfNames);

            }



            // eg:

            // def foo(*args): print args            

            // __metaclass__ = foo

            // class bar: pass

            // calls our function...

            PythonContext pc = PythonContext.GetContext(context);



            return pc.MetaClassCallSite.Target(

                pc.MetaClassCallSite,

                context,

                metaclass,

                name,

                tupleBases,

                vars

            );

        }



        /// <summary>

        /// Python runtime helper for raising assertions. Used by AssertStatement.

        /// </summary>

        /// <param name="msg">Object representing the assertion message</param>

        public static void RaiseAssertionError(object msg) {

            if (msg == null) {

                throw PythonOps.AssertionError(String.Empty, ArrayUtils.EmptyObjects);

            } else {

                string message = PythonOps.ToString(msg);

                throw PythonOps.AssertionError("{0}", new object[] { message });

            }



        }



        /// <summary>

        /// Python runtime helper to create instance of Python List object.

        /// </summary>

        /// <returns>New instance of List</returns>

        public static List MakeList() {

            return new List();

        }



        /// <summary>

        /// Python runtime helper to create a populated instance of Python List object.

        /// </summary>

        public static List MakeList(params object[] items) {

            return new List(items);

        }



        /// <summary>

        /// Python runtime helper to create a populated instance of Python List object w/o

        /// copying the array contents.

        /// </summary>

        [NoSideEffects]

        public static List MakeListNoCopy(params object[] items) {

            return List.FromArrayNoCopy(items);

        }



        /// <summary>

        /// Python runtime helper to create a populated instance of Python List object.

        /// 

        /// List is populated by arbitrary user defined object.

        /// </summary>

        public static List MakeListFromSequence(object sequence) {

            return new List(sequence);

        }



        /// <summary>

        /// Python runtime helper to create an instance of Python List object.

        /// 

        /// List has the initial provided capacity.

        /// </summary>

        [NoSideEffects]

        public static List MakeEmptyList(int capacity) {

            return new List(capacity);

        }



        [NoSideEffects]

        public static List MakeEmptyListFromCode() {

            return List.FromArrayNoCopy(ArrayUtils.EmptyObjects);

        }



        /// <summary>

        /// Python runtime helper to create an instance of Tuple

        /// </summary>

        /// <param name="items"></param>

        /// <returns></returns>

        [NoSideEffects]

        public static PythonTuple MakeTuple(params object[] items) {

            return PythonTuple.MakeTuple(items);

        }



        /// <summary>

        /// Python runtime helper to create an instance of Tuple

        /// </summary>

        /// <param name="items"></param>

        [NoSideEffects]

        public static PythonTuple MakeTupleFromSequence(object items) {

            return PythonTuple.Make(items);

        }



        /// <summary>

        /// Python Runtime Helper for enumerator unpacking (tuple assignments, ...)

        /// Creates enumerator from the input parameter e, and then extracts 

        /// expected number of values, returning them as array

        /// 

        /// If the input is a Python tuple returns the tuples underlying data array.  Callers

        /// should not mutate the resulting tuple.

        /// </summary>

        /// <param name="context">The code context of the AST getting enumerator values.</param>

        /// <param name="e">object to enumerate</param>

        /// <param name="expected">expected number of objects to extract from the enumerator</param>

        /// <returns>

        /// array of objects (.Lengh == expected) if exactly expected objects are in the enumerator.

        /// Otherwise throws exception

        /// </returns>

        [LightThrowing]

        public static object GetEnumeratorValues(CodeContext/*!*/ context, object e, int expected) {

            if (e != null && e.GetType() == typeof(PythonTuple)) {

                // fast path for tuples, avoid enumerating & copying the tuple.

                return GetEnumeratorValuesFromTuple((PythonTuple)e, expected);

            }



            IEnumerator ie = PythonOps.GetEnumeratorForUnpack(context, e);



            int count = 0;

            object[] values = new object[expected];



            while (count < expected) {

                if (!ie.MoveNext()) {

                    return LightExceptions.Throw(PythonOps.ValueErrorForUnpackMismatch(expected, count));

                }

                values[count] = ie.Current;

                count++;

            }



            if (ie.MoveNext()) {

                return LightExceptions.Throw(PythonOps.ValueErrorForUnpackMismatch(expected, count + 1));

            }



            return values;

        }



        [LightThrowing]

        public static object GetEnumeratorValuesNoComplexSets(CodeContext/*!*/ context, object e, int expected) {

            if (e != null && e.GetType() == typeof(List)) {

                // fast path for lists, avoid enumerating & copying the list.

                return GetEnumeratorValuesFromList((List)e, expected);

            }



            return GetEnumeratorValues(context, e, expected);

        }



        [LightThrowing]

        private static object GetEnumeratorValuesFromTuple(PythonTuple pythonTuple, int expected) {

            if (pythonTuple.Count == expected) {

                return pythonTuple._data;

            }



            return LightExceptions.Throw(PythonOps.ValueErrorForUnpackMismatch(expected, pythonTuple.Count));

        }



        private static object[] GetEnumeratorValuesFromList(List list, int expected) {

            if (list._size == expected) {

                return list._data;

            }



            throw PythonOps.ValueErrorForUnpackMismatch(expected, list._size);

        }

        /// <summary>

        /// Python runtime helper to create instance of Slice object

        /// </summary>

        /// <param name="start">Start of the slice.</param>

        /// <param name="stop">End of the slice.</param>

        /// <param name="step">Step of the slice.</param>

        /// <returns>Slice</returns>

        public static Slice MakeSlice(object start, object stop, object step) {

            return new Slice(start, stop, step);

        }



        #region Standard I/O support



        public static void Write(CodeContext/*!*/ context, object f, string text) {

            PythonContext pc = PythonContext.GetContext(context);



            if (f == null) {

                f = pc.SystemStandardOut;

            }

            if (f == null || f == Uninitialized.Instance) {

                throw PythonOps.RuntimeError("lost sys.stdout");

            }



            PythonFile pf = f as PythonFile;

            if (pf != null) {

                // avoid spinning up a site in the normal case

                pf.write(text);

                return;

            }



            pc.WriteCallSite.Target(

                pc.WriteCallSite,

                context,

                GetBoundAttr(context, f, "write"),

                text

            );

        }



        private static object ReadLine(CodeContext/*!*/ context, object f) {

            if (f == null || f == Uninitialized.Instance) throw PythonOps.RuntimeError("lost sys.std_in");

            return PythonOps.Invoke(context, f, "readline");

        }



        public static void WriteSoftspace(CodeContext/*!*/ context, object f) {

            if (CheckSoftspace(f)) {

                SetSoftspace(f, ScriptingRuntimeHelpers.False);

                Write(context, f, " ");

            }

        }



        public static void SetSoftspace(object f, object value) {

            PythonOps.SetAttr(DefaultContext.Default, f, "softspace", value);

        }



        public static bool CheckSoftspace(object f) {

            PythonFile pf = f as PythonFile;

            if (pf != null) {

                // avoid spinning up a site in the common case

                return pf.softspace;

            }



            object result;

            if (PythonOps.TryGetBoundAttr(f, "softspace", out result)) {

                return PythonOps.IsTrue(result);

            }



            return false;

        }



        // Must stay here for now because libs depend on it.

        public static void Print(CodeContext/*!*/ context, object o) {

            PrintWithDest(context, PythonContext.GetContext(context).SystemStandardOut, o);

        }



        public static void PrintNoNewline(CodeContext/*!*/ context, object o) {

            PrintWithDestNoNewline(context, PythonContext.GetContext(context).SystemStandardOut, o);

        }



        public static void PrintWithDest(CodeContext/*!*/ context, object dest, object o) {

            PrintWithDestNoNewline(context, dest, o);

            Write(context, dest, "\n");

        }



        public static void PrintWithDestNoNewline(CodeContext/*!*/ context, object dest, object o) {

            WriteSoftspace(context, dest);

            Write(context, dest, o == null ? "None" : ToString(o));

        }



        public static object ReadLineFromSrc(CodeContext/*!*/ context, object src) {

            return ReadLine(context, src);

        }



        /// <summary>

        /// Prints newline into default standard output

        /// </summary>

        public static void PrintNewline(CodeContext/*!*/ context) {

            PrintNewlineWithDest(context, PythonContext.GetContext(context).SystemStandardOut);

        }



        /// <summary>

        /// Prints newline into specified destination. Sets softspace property to false.

        /// </summary>

        public static void PrintNewlineWithDest(CodeContext/*!*/ context, object dest) {

            PythonOps.Write(context, dest, "\n");

            PythonOps.SetSoftspace(dest, ScriptingRuntimeHelpers.False);

        }



        /// <summary>

        /// Prints value into default standard output with Python comma semantics.

        /// </summary>

        public static void PrintComma(CodeContext/*!*/ context, object o) {

            PrintCommaWithDest(context, PythonContext.GetContext(context).SystemStandardOut, o);

        }



        /// <summary>

        /// Prints value into specified destination with Python comma semantics.

        /// </summary>

        public static void PrintCommaWithDest(CodeContext/*!*/ context, object dest, object o) {

            PythonOps.WriteSoftspace(context, dest);

            string s = o == null ? "None" : PythonOps.ToString(o);



            PythonOps.Write(context, dest, s);

            PythonOps.SetSoftspace(dest, !s.EndsWith("\n"));

        }



        /// <summary>

        /// Called from generated code when we are supposed to print an expression value

        /// </summary>

        public static void PrintExpressionValue(CodeContext/*!*/ context, object value) {

            PythonContext pc = PythonContext.GetContext(context);

            object dispHook = pc.GetSystemStateValue("displayhook");

            pc.CallWithContext(context, dispHook, value);

        }



#if !SILVERLIGHT

        public static void PrintException(CodeContext/*!*/ context, Exception/*!*/ exception, IConsole console) {

            PythonContext pc = PythonContext.GetContext(context);

            PythonTuple exInfo = GetExceptionInfoLocal(context, exception);

            pc.SetSystemStateValue("last_type", exInfo[0]);

            pc.SetSystemStateValue("last_value", exInfo[1]);

            pc.SetSystemStateValue("last_traceback", exInfo[2]);



            object exceptHook = pc.GetSystemStateValue("excepthook");

            BuiltinFunction bf = exceptHook as BuiltinFunction;

            if (console != null && bf != null && bf.DeclaringType == typeof(SysModule) && bf.Name == "excepthook") {

                // builtin except hook, display it to the console which may do nice coloring

                console.WriteLine(pc.FormatException(exception), Style.Error);

            } else {

                // user defined except hook or no console

                try {

                    PythonCalls.Call(context, exceptHook, exInfo[0], exInfo[1], exInfo[2]);

                } catch (Exception e) {

                    PrintWithDest(context, pc.SystemStandardError, "Error in sys.excepthook:");

                    PrintWithDest(context, pc.SystemStandardError, pc.FormatException(e));

                    PrintNewlineWithDest(context, pc.SystemStandardError);



                    PrintWithDest(context, pc.SystemStandardError, "Original exception was:");

                    PrintWithDest(context, pc.SystemStandardError, pc.FormatException(exception));

                }

            }

        }

#endif



        #endregion



        #region Import support



        /// <summary>

        /// Called from generated code for:

        /// 

        /// import spam.eggs

        /// </summary>

        [ProfilerTreatsAsExternal, LightThrowing]

        public static object ImportTop(CodeContext/*!*/ context, string fullName, int level) {

            return Importer.ImportLightThrow(context, fullName, null, level);

        }



        /// <summary>

        /// Python helper method called from generated code for:

        /// 

        /// import spam.eggs as ham

        /// </summary>

        [ProfilerTreatsAsExternal, LightThrowing]

        public static object ImportBottom(CodeContext/*!*/ context, string fullName, int level) {

            object module = Importer.ImportLightThrow(context, fullName, null, level);



            if (fullName.IndexOf('.') >= 0) {

                // Extract bottom from the imported module chain

                string[] parts = fullName.Split('.');



                for (int i = 1; i < parts.Length; i++) {

                    module = PythonOps.GetBoundAttr(context, module, parts[i]);

                }

            }

            return module;

        }



        /// <summary>

        /// Called from generated code for:

        /// 

        /// from spam import eggs1, eggs2 

        /// </summary>

        [ProfilerTreatsAsExternal, LightThrowing]

        public static object ImportWithNames(CodeContext/*!*/ context, string fullName, string[] names, int level) {

            return Importer.ImportLightThrow(context, fullName, PythonTuple.MakeTuple(names), level);

        }





        /// <summary>

        /// Imports one element from the module in the context of:

        /// 

        /// from module import a, b, c, d

        /// 

        /// Called repeatedly for all elements being imported (a, b, c, d above)

        /// </summary>

        public static object ImportFrom(CodeContext/*!*/ context, object module, string name) {

            return Importer.ImportFrom(context, module, name);

        }



        /// <summary>

        /// Called from generated code for:

        /// 

        /// from spam import *

        /// </summary>

        [ProfilerTreatsAsExternal]

        public static void ImportStar(CodeContext/*!*/ context, string fullName, int level) {

            object newmod = Importer.Import(context, fullName, PythonTuple.MakeTuple("*"), level);



            PythonModule scope = newmod as PythonModule;

            NamespaceTracker nt = newmod as NamespaceTracker;

            PythonType pt = newmod as PythonType;



            if (pt != null &&

                !pt.UnderlyingSystemType.IsEnum &&

                (!pt.UnderlyingSystemType.IsAbstract || !pt.UnderlyingSystemType.IsSealed)) {

                // from type import * only allowed on static classes (and enums)

                throw PythonOps.ImportError("no module named {0}", pt.Name);

            }



            IEnumerator exports;

            object all;

            bool filterPrivates = false;



            // look for __all__, if it's defined then use that to get the attribute names,

            // otherwise get all the names and filter out members starting w/ _'s.

            if (PythonOps.TryGetBoundAttr(context, newmod, "__all__", out all)) {

                exports = PythonOps.GetEnumerator(all);

            } else {

                exports = PythonOps.GetAttrNames(context, newmod).GetEnumerator();

                filterPrivates = true;

            }



            // iterate through the names and populate the scope with the values.

            while (exports.MoveNext()) {

                string name = exports.Current as string;

                if (name == null) {

                    throw PythonOps.TypeErrorForNonStringAttribute();

                } else if (filterPrivates && name.Length > 0 && name[0] == '_') {

                    continue;

                }



                // we special case several types to avoid one-off code gen of dynamic sites                

                if (scope != null) {

                    context.SetVariable(name, scope.__dict__[name]);

                } else if (nt != null) {

                    object value = NamespaceTrackerOps.GetCustomMember(context, nt, name);

                    if (value != OperationFailed.Value) {

                        context.SetVariable(name, value);

                    }

                } else if (pt != null) {

                    PythonTypeSlot pts;

                    object value;

                    if (pt.TryResolveSlot(context, name, out pts) &&

                        pts.TryGetValue(context, null, pt, out value)) {

                        context.SetVariable(name, value);

                    }

                } else {

                    // not a known type, we'll do use a site to do the get...

                    context.SetVariable(name, PythonOps.GetBoundAttr(context, newmod, name));

                }

            }

        }



        #endregion



        #region Exec



        /// <summary>

        /// Unqualified exec statement support.

        /// A Python helper which will be called for the statement:

        /// 

        /// exec code

        /// </summary>

        [ProfilerTreatsAsExternal]

        public static void UnqualifiedExec(CodeContext/*!*/ context, object code) {

            PythonDictionary locals = null;

            PythonDictionary globals = null;



            // if the user passes us a tuple we'll extract the 3 values out of it            

            PythonTuple codeTuple = code as PythonTuple;

            if (codeTuple != null && codeTuple.__len__() > 0 && codeTuple.__len__() <= 3) {

                code = codeTuple[0];



                if (codeTuple.__len__() > 1 && codeTuple[1] != null) {

                    globals = codeTuple[1] as PythonDictionary;

                    if (globals == null) throw PythonOps.TypeError("globals must be dictionary or none");

                }



                if (codeTuple.__len__() > 2 && codeTuple[2] != null) {

                    locals = codeTuple[2] as PythonDictionary;

                    if (locals == null) throw PythonOps.TypeError("locals must be dictionary or none");

                } else {

                    locals = globals;

                }

            }



            QualifiedExec(context, code, globals, locals);

        }



        /// <summary>

        /// Qualified exec statement support,

        /// Python helper which will be called for the statement:

        /// 

        /// exec code in globals [, locals ]

        /// </summary>

        [ProfilerTreatsAsExternal]

        public static void QualifiedExec(CodeContext/*!*/ context, object code, PythonDictionary globals, object locals) {

            PythonFile pf;

            Stream cs;



            var pythonContext = PythonContext.GetContext(context);



            bool noLineFeed = true;



            // TODO: use ContentProvider?

            if ((pf = code as PythonFile) != null) {

                List lines = pf.readlines();



                StringBuilder fullCode = new StringBuilder();

                for (int i = 0; i < lines.__len__(); i++) {

                    fullCode.Append(lines[i]);

                }



                code = fullCode.ToString();

            } else if ((cs = code as Stream) != null) {



                using (StreamReader reader = new StreamReader(cs)) { // TODO: encoding? 

                    code = reader.ReadToEnd();

                }



                noLineFeed = false;

            }



            string strCode = code as string;



            if (strCode != null) {

                SourceUnit source;



                if (noLineFeed) {

                    source = pythonContext.CreateSourceUnit(new NoLineFeedSourceContentProvider(strCode), "<string>", SourceCodeKind.Statements);

                } else {

                    source = pythonContext.CreateSnippet(strCode, SourceCodeKind.Statements);

                }



                PythonCompilerOptions compilerOptions = Builtin.GetRuntimeGeneratedCodeCompilerOptions(context, true, 0);



                // do interpretation only on strings -- not on files, streams, or code objects

                code = FunctionCode.FromSourceUnit(source, compilerOptions, false);

            }



            FunctionCode fc = code as FunctionCode;

            if (fc == null) {

                throw PythonOps.TypeError("arg 1 must be a string, file, Stream, or code object, not {0}", PythonTypeOps.GetName(code));

            }



            if (locals == null) locals = globals;

            if (globals == null) globals = context.GlobalDict;



            if (locals != null && PythonOps.IsMappingType(context, locals) != ScriptingRuntimeHelpers.True) {

                throw PythonOps.TypeError("exec: arg 3 must be mapping or None");

            }



            CodeContext execContext = Builtin.GetExecEvalScope(context, globals, Builtin.GetAttrLocals(context, locals), true, false);

            if (context.LanguageContext.PythonOptions.Frames) {

                List<FunctionStack> stack = PushFrame(execContext, fc);

                try {

                    fc.Call(execContext);

                } finally {

                    stack.RemoveAt(stack.Count - 1);

                }

            } else {

                fc.Call(execContext);

            }

        }



        #endregion



        public static ICollection GetCollection(object o) {

            ICollection ret = o as ICollection;

            if (ret != null) return ret;



            List<object> al = new List<object>();

            IEnumerator e = GetEnumerator(o);

            while (e.MoveNext()) al.Add(e.Current);

            return al;

        }



        public static IEnumerator GetEnumerator(object o) {

            return GetEnumerator(DefaultContext.Default, o);

        }



        public static IEnumerator GetEnumerator(CodeContext/*!*/ context, object o) {

            IEnumerator ie;

            if (!TryGetEnumerator(context, o, out ie)) {

                throw PythonOps.TypeError("{0} is not iterable", PythonTypeOps.GetName(o));

            }

            return ie;

        }



        // Lack of type restrictions allows this method to return the direct result of __iter__ without

        // wrapping it. This is the proper behavior for Builtin.iter().

        public static object GetEnumeratorObject(CodeContext/*!*/ context, object o) {

            object iterFunc;

            if (PythonOps.TryGetBoundAttr(context, o, "__iter__", out iterFunc) &&

                !Object.ReferenceEquals(iterFunc, NotImplementedType.Value)) {

                return PythonOps.CallWithContext(context, iterFunc);

            }



            return GetEnumerator(context, o);

        }



        public static IEnumerator GetEnumeratorForUnpack(CodeContext/*!*/ context, object enumerable) {

            IEnumerator enumerator;

            if (!TryGetEnumerator(context, enumerable, out enumerator)) {

                throw TypeErrorForNotIterable(enumerable);

            }



            return enumerator;

        }



        public static Exception TypeErrorForNotIterable(object enumerable) {

            return PythonOps.TypeError("'{0}' object is not iterable", PythonTypeOps.GetName(enumerable));

        }        



        public static KeyValuePair<IEnumerator, IDisposable> ThrowTypeErrorForBadIteration(CodeContext/*!*/ context, object enumerable) {

            throw PythonOps.TypeError("iteration over non-sequence of type {0}", PythonTypeOps.GetName(enumerable));

        }



        internal static bool TryGetEnumerator(CodeContext/*!*/ context, object enumerable, out IEnumerator enumerator) {

            enumerator = null;

            IEnumerable enumer;

            if (PythonContext.GetContext(context).TryConvertToIEnumerable(enumerable, out enumer)) {

                enumerator = enumer.GetEnumerator();

                return true;

            }



            return false;

        }



        public static void ForLoopDispose(KeyValuePair<IEnumerator, IDisposable> iteratorInfo) {

            if (iteratorInfo.Value != null) {

                iteratorInfo.Value.Dispose();

            }

        }



        public static KeyValuePair<IEnumerator, IDisposable> StringEnumerator(string str) {

            return new KeyValuePair<IEnumerator, IDisposable>(StringOps.StringEnumerator(str), null);

        }



        public static KeyValuePair<IEnumerator, IDisposable> BytesEnumerator(IList<byte> bytes) {

            return new KeyValuePair<IEnumerator, IDisposable>(IListOfByteOps.BytesEnumerator(bytes), null);

        }



        public static KeyValuePair<IEnumerator, IDisposable> BytesIntEnumerator(IList<byte> bytes) {

            return new KeyValuePair<IEnumerator, IDisposable>(IListOfByteOps.BytesIntEnumerator(bytes), null);

        }



        public static KeyValuePair<IEnumerator, IDisposable> GetEnumeratorFromEnumerable(IEnumerable enumerable) {

            IEnumerator enumerator = enumerable.GetEnumerator();

            return new KeyValuePair<IEnumerator, IDisposable>(enumerator, enumerator as IDisposable);

        }



        public static IEnumerable StringEnumerable(string str) {

            return StringOps.StringEnumerable(str);

        }



        public static IEnumerable BytesEnumerable(IList<byte> bytes) {

            return IListOfByteOps.BytesEnumerable(bytes);

        }



        public static IEnumerable BytesIntEnumerable(IList<byte> bytes) {

            return IListOfByteOps.BytesIntEnumerable(bytes);

        }



        #region Exception handling



        // The semantics here are:

        // 1. Each thread has a "current exception", which is returned as a tuple by sys.exc_info().

        // 2. The current exception is set on encountering an except block, even if the except block doesn't

        //    match the exception.

        // 3. Each function on exit (either via exception, return, or yield) will restore the "current exception" 

        //    to the value it had on function-entry. 

        //

        // So common codegen would be:

        // 

        // function() {

        //   $save = SaveCurrentException();

        //   try { 

        //      def foo():

        //              try:

        //              except:

        //                  SetCurrentException($exception)

        //                  <except body>

        //   

        //   finally {

        //      RestoreCurrentException($save)

        //   }



        // Called at the start of the except handlers to set the current exception. 

        public static object SetCurrentException(CodeContext/*!*/ context, Exception/*!*/ clrException) {

            Assert.NotNull(clrException);



            // we need to extract before we check because ThreadAbort.ExceptionState is cleared after

            // we reset the abort.

            object res = PythonExceptions.ToPython(clrException);



#if !SILVERLIGHT

            // Check for thread abort exceptions.

            // This is necessary to be able to catch python's KeyboardInterrupt exceptions.

            // CLR restrictions require that this must be called from within a catch block.  This gets

            // called even if we aren't going to handle the exception - we'll just reset the abort 

            ThreadAbortException tae = clrException as ThreadAbortException;

            if (tae != null && tae.ExceptionState is KeyboardInterruptException) {

                Thread.ResetAbort();

            }

#endif



            RawException = clrException;

            return res;

        }



        /// <summary>

        /// Called from generated code at the start of a catch block.

        /// </summary>

        public static void BuildExceptionInfo(CodeContext/*!*/ context, Exception clrException) {

            object pyExcep = PythonExceptions.ToPython(clrException);

            List<DynamicStackFrame> frames = clrException.GetFrameList();

            IPythonObject pyObj = pyExcep as IPythonObject;



            object excType;

            if (pyObj != null) {

                // class is always the Python type for new-style types (this is also the common case)

                excType = pyObj.PythonType;

            } else {

                excType = PythonOps.GetBoundAttr(context, pyExcep, "__class__");

            }



            context.LanguageContext.UpdateExceptionInfo(clrException, excType, pyExcep, frames);

        }



        // Clear the current exception. Most callers should restore the exception.

        // This is mainly for sys.exc_clear()        

        public static void ClearCurrentException() {

            RestoreCurrentException(null);

        }



        public static void ExceptionHandled(CodeContext context) {

            var pyCtx = context.LanguageContext;



            pyCtx.ExceptionHandled();

        }



        // Called by code-gen to save it. Codegen just needs to pass this back to RestoreCurrentException.

        public static Exception SaveCurrentException() {

            return RawException;

        }



        // Called at function exit (like popping). Pass value from SaveCurrentException.

        public static void RestoreCurrentException(Exception clrException) {

            RawException = clrException;

        }



        public static object CheckException(CodeContext/*!*/ context, object exception, object test) {

            Debug.Assert(exception != null);



            ObjectException objex;



            if ((objex = exception as ObjectException) != null) {

                if (PythonOps.IsSubClass(context, objex.Type, test)) {

                    return objex.Instance;

                }

                return null;

            } else if (test is PythonType) {

                if (PythonOps.IsSubClass(test as PythonType, TypeCache.BaseException)) {

                    // catching a Python exception type explicitly.

                    if (PythonOps.IsInstance(context, exception, test)) return exception;

                } else if (PythonOps.IsSubClass(test as PythonType, DynamicHelpers.GetPythonTypeFromType(typeof(Exception)))) {

                    // catching a CLR exception type explicitly.

                    Exception clrEx = PythonExceptions.ToClr(exception);

                    if (PythonOps.IsInstance(context, clrEx, test)) return clrEx;

                }

            } else if (test is PythonTuple) {

                // we handle multiple exceptions, we'll check them one at a time.

                PythonTuple tt = test as PythonTuple;

                for (int i = 0; i < tt.__len__(); i++) {

                    object res = CheckException(context, exception, tt[i]);

                    if (res != null) return res;

                }

            } else if (test is OldClass) {

                if (PythonOps.IsInstance(context, exception, test)) {

                    // catching a Python type.

                    return exception;

                }

            }



            return null;

        }



        private static TraceBack CreateTraceBack(PythonContext pyContext, Exception e) {

            // user provided trace back

            var tb = e.GetTraceBack();

            if (tb != null) {

                return tb;

            }



            IList<DynamicStackFrame> frames = ((IList<DynamicStackFrame>)e.GetFrameList()) ?? new DynamicStackFrame[0];

            return CreateTraceBack(e, frames, frames.Count);

        }



        internal static TraceBack CreateTraceBack(Exception e, IList<DynamicStackFrame> frames, int frameCount) {

            TraceBack tb  = null;

            for (int i = 0; i < frameCount; i++) {

                DynamicStackFrame frame = frames[i];



                string name = frame.GetMethodName();

                if (name.IndexOf('#') > 0) {

                    // dynamic method, strip the trailing id...

                    name = name.Substring(0, name.IndexOf('#'));

                }



                PythonDynamicStackFrame pyFrame = frame as PythonDynamicStackFrame;

                if (pyFrame != null) {

                    CodeContext context = pyFrame.CodeContext;

                    FunctionCode code = pyFrame.Code;



                    TraceBackFrame tbf = new TraceBackFrame(

                        context,

                        context.GlobalDict,

                        context.Dict,

                        code);



                    tb = new TraceBack(tb, tbf);

                    tb.SetLine(frame.GetFileLineNumber());

                }

            }



            e.SetTraceBack(tb);

            return tb;

        }



        /// <summary>

        /// Get an exception tuple for the "current" exception. This is used for sys.exc_info()

        /// </summary>

        public static PythonTuple GetExceptionInfo(CodeContext/*!*/ context) {

            return GetExceptionInfoLocal(context, RawException);

        }



        /// <summary>

        /// Get an exception tuple for a given exception. This is like the inverse of MakeException.

        /// </summary>

        /// <param name="context">the code context</param>

        /// <param name="ex">the exception to create a tuple for.</param>

        /// <returns>a tuple of (type, value, traceback)</returns>

        /// <remarks>This is called directly by the With statement so that it can get an exception tuple

        /// in its own private except handler without disturbing the thread-wide sys.exc_info(). </remarks>

        public static PythonTuple/*!*/ GetExceptionInfoLocal(CodeContext/*!*/ context, Exception ex) {

            if (ex == null) {

                return PythonTuple.MakeTuple(null, null, null);

            }



            PythonContext pc = context.LanguageContext;



            object pyExcep = PythonExceptions.ToPython(ex);

            TraceBack tb = CreateTraceBack(pc, ex);



            IPythonObject pyObj = pyExcep as IPythonObject;

            object excType;

            if (pyObj != null) {

                // class is always the Python type for new-style types (this is also the common case)

                excType = pyObj.PythonType;

            } else {

                excType = PythonOps.GetBoundAttr(context, pyExcep, "__class__");

            }



            pc.UpdateExceptionInfo(excType, pyExcep, tb);



            return PythonTuple.MakeTuple(excType, pyExcep, tb);

        }



        /// <summary>

        /// helper function for re-raised exceptions.

        /// </summary>

        public static Exception MakeRethrownException(CodeContext/*!*/ context) {

            PythonTuple t = GetExceptionInfo(context);



            Exception e = MakeExceptionWorker(context, t[0], t[1], t[2], true);

            return MakeRethrowExceptionWorker(e);

        }



        public static Exception MakeRethrowExceptionWorker(Exception e) {

            e.RemoveTraceBack();

            ExceptionHelpers.UpdateForRethrow(e);

            return e;

        }



        /// <summary>

        /// helper function for non-re-raise exceptions.

        /// 

        /// type is the type of exception to throw or an instance.  If it 

        /// is an instance then value should be null.  

        /// 

        /// If type is a type then value can either be an instance of type,

        /// a Tuple, or a single value.  This case is handled by EC.CreateThrowable.

        /// </summary>

        public static Exception MakeException(CodeContext/*!*/ context, object type, object value, object traceback) {

            Exception e = MakeExceptionWorker(context, type, value, traceback, false);

            e.RemoveFrameList();

            return e;

        }



        private static Exception MakeExceptionWorker(CodeContext/*!*/ context, object type, object value, object traceback, bool forRethrow) {

            Exception throwable;

            PythonType pt;



            if (type is PythonExceptions.BaseException) {

                throwable = PythonExceptions.ToClr(type);

            } else if (type is Exception) {

                throwable = type as Exception;

            } else if ((pt = type as PythonType) != null && typeof(PythonExceptions.BaseException).IsAssignableFrom(pt.UnderlyingSystemType)) {

                throwable = PythonExceptions.CreateThrowableForRaise(context, pt, value);

            } else if (type is OldClass) {

                if (value == null) {

                    throwable = new OldInstanceException((OldInstance)PythonCalls.Call(context, type));

                } else {

                    throwable = PythonExceptions.CreateThrowableForRaise(context, (OldClass)type, value);

                }

            } else if (type is OldInstance) {

                throwable = new OldInstanceException((OldInstance)type);

            } else {

                throwable = MakeExceptionTypeError(type);

            }



            if (traceback != null) {

                if (!forRethrow) {

                    TraceBack tb = traceback as TraceBack;

                    if (tb == null) throw PythonOps.TypeError("traceback argument must be a traceback object");



                    throwable.SetTraceBack(tb);

                }

            } else {

                throwable.RemoveTraceBack();

            }



            PerfTrack.NoteEvent(PerfTrack.Categories.Exceptions, throwable);



            return throwable;

        }



        public static Exception CreateThrowable(PythonType type, params object[] args) {

            return PythonExceptions.CreateThrowable(type, args);

        }



        #endregion



        public static string[] GetFunctionSignature(PythonFunction function) {

            return new string[] { function.GetSignatureString() };

        }



        public static PythonDictionary CopyAndVerifyDictionary(PythonFunction function, IDictionary dict) {

            foreach (object o in dict.Keys) {

                if (!(o is string)) {

                    throw TypeError("{0}() keywords must be strings", function.__name__);

                }

            }

            return new PythonDictionary(dict);

        }



        public static PythonDictionary/*!*/ CopyAndVerifyUserMapping(PythonFunction/*!*/ function, object dict) {

            return UserMappingToPythonDictionary(function.Context, dict, function.func_name);

        }



        public static PythonDictionary UserMappingToPythonDictionary(CodeContext/*!*/ context, object dict, string funcName) {

            // call dict.keys()

            object keys;

            if (!PythonTypeOps.TryInvokeUnaryOperator(context, dict, "keys", out keys)) {

                throw PythonOps.TypeError("{0}() argument after ** must be a mapping, not {1}",

                    funcName,

                    PythonTypeOps.GetName(dict));

            }



            PythonDictionary res = new PythonDictionary();



            // enumerate the keys getting their values

            IEnumerator enumerator = GetEnumerator(keys);

            while (enumerator.MoveNext()) {

                object o = enumerator.Current;

                string s = o as string;

                if (s == null) {

                    Extensible<string> es = o as Extensible<string>;

                    if (es == null) {

                        throw PythonOps.TypeError("{0}() keywords must be strings, not {0}",

                            funcName,

                            PythonTypeOps.GetName(dict));

                    }



                    s = es.Value;

                }



                res[o] = PythonOps.GetIndex(context, dict, o);

            }



            return res;

        }



        public static PythonDictionary CopyAndVerifyPythonDictionary(PythonFunction function, PythonDictionary dict) {

            if (dict._storage.HasNonStringAttributes()) {

                throw TypeError("{0}() keywords must be strings", function.__name__);

            }



            return new PythonDictionary(dict);

        }



        public static object ExtractDictionaryArgument(PythonFunction function, string name, int argCnt, PythonDictionary dict) {

            object val;

            if (dict.TryGetValue(name, out val)) {

                dict.Remove(name);

                return val;

            }



            throw PythonOps.TypeError("{0}() takes exactly {1} arguments ({2} given)",

                function.__name__,

                function.NormalArgumentCount,

                argCnt);

        }



        public static void AddDictionaryArgument(PythonFunction function, string name, object value, PythonDictionary dict) {

            if (dict.ContainsKey(name)) {

                throw MultipleKeywordArgumentError(function, name);

            }



            dict[name] = value;

        }



        public static void VerifyUnduplicatedByPosition(PythonFunction function, string name, int position, int listlen) {

            if (listlen > 0 && listlen > position) {

                throw MultipleKeywordArgumentError(function, name);

            }

        }



        public static List CopyAndVerifyParamsList(PythonFunction function, object list) {

            return new List(list);

        }



        public static PythonTuple GetOrCopyParamsTuple(PythonFunction function, object input) {

            if (input == null) {

                throw PythonOps.TypeError("{0}() argument after * must be a sequence, not NoneType", function.func_name);

            } else if (input.GetType() == typeof(PythonTuple)) {

                return (PythonTuple)input;

            }



            return PythonTuple.Make(input);

        }



        public static object ExtractParamsArgument(PythonFunction function, int argCnt, List list) {

            if (list.__len__() != 0) {

                return list.pop(0);

            }



            throw function.BadArgumentError(argCnt);

        }



        public static void AddParamsArguments(List list, params object[] args) {

            for (int i = 0; i < args.Length; i++) {

                list.insert(i, args[i]);

            }

        }



        /// <summary>

        /// Extracts an argument from either the dictionary or params

        /// </summary>

        public static object ExtractAnyArgument(PythonFunction function, string name, int argCnt, List list, IDictionary dict) {

            object val;

            if (dict.Contains(name)) {

                if (list.__len__() != 0) {

                    throw MultipleKeywordArgumentError(function, name);

                }

                val = dict[name];

                dict.Remove(name);

                return val;

            }



            if (list.__len__() != 0) {

                return list.pop(0);

            }



            if (function.ExpandDictPosition == -1 && dict.Count > 0) {

                // python raises an error for extra splatted kw keys before missing arguments.

                // therefore we check for this in the error case here.

                foreach (string x in dict.Keys) {

                    bool found = false;

                    foreach (string y in function.ArgNames) {

                        if (x == y) {

                            found = true;

                            break;

                        }

                    }



                    if (!found) {

                        throw UnexpectedKeywordArgumentError(function, x);

                    }

                }

            }



            throw BinderOps.TypeErrorForIncorrectArgumentCount(

                function.__name__,

                function.NormalArgumentCount,

                function.Defaults.Length,

                argCnt,

                function.ExpandListPosition != -1,

                dict.Count > 0);

        }



        public static ArgumentTypeException SimpleTypeError(string message) {

            return new TypeErrorException(message);

        }

        

        public static object GetParamsValueOrDefault(PythonFunction function, int index, List extraArgs) {

            if (extraArgs.__len__() > 0) {

                return extraArgs.pop(0);

            }



            return function.Defaults[index];

        }



        public static object GetFunctionParameterValue(PythonFunction function, int index, string name, List extraArgs, PythonDictionary dict) {

            if (extraArgs != null && extraArgs.__len__() > 0) {

                return extraArgs.pop(0);

            }



            object val;

            if (dict != null && dict.TryRemoveValue(name, out val)) {

                return val;

            }



            return function.Defaults[index];

        }



        public static void CheckParamsZero(PythonFunction function, List extraArgs) {

            if (extraArgs.__len__() != 0) {

                throw function.BadArgumentError(extraArgs.__len__() + function.NormalArgumentCount);

            }

        }



        public static void CheckUserParamsZero(PythonFunction function, object sequence) {

            int len = PythonOps.Length(sequence);

            if (len != 0) {

                throw function.BadArgumentError(len + function.NormalArgumentCount);

            }

        }



        public static void CheckDictionaryZero(PythonFunction function, IDictionary dict) {

            if (dict.Count != 0) {

                IDictionaryEnumerator ie = dict.GetEnumerator();

                ie.MoveNext();



                throw UnexpectedKeywordArgumentError(function, (string)ie.Key);

            }

        }



        public static bool CheckDictionaryMembers(PythonDictionary dict, string[] names) {

            if (dict.Count != names.Length) {

                return false;

            }



            foreach (string name in names) {

                if (!dict.ContainsKey(name)) {

                    return false;

                }

            }



            return true;

        }



        public static object PythonFunctionGetMember(PythonFunction function, string name) {

            object res;

            if (function._dict != null && function._dict.TryGetValue(name, out res)) {

                return res;

            }



            return OperationFailed.Value;

        }



        public static object PythonFunctionSetMember(PythonFunction function, string name, object value) {

            return function.__dict__[name] = value;

        }



        public static void PythonFunctionDeleteDict() {

            throw PythonOps.TypeError("function's dictionary may not be deleted");

        }



        public static void PythonFunctionDeleteDoc(PythonFunction function) {

            function.__doc__ = null;

        }



        public static void PythonFunctionDeleteDefaults(PythonFunction function) {

            function.__defaults__ = null;

        }



        public static bool PythonFunctionDeleteMember(PythonFunction function, string name) {

            if (function._dict == null) return false;



            return function._dict.Remove(name);

        }



        /// <summary>

        /// Creates a new array the values set to Uninitialized.Instance.  The array

        /// is large enough to hold for all of the slots allocated for the type and

        /// its sub types.

        /// </summary>

        public static object[] InitializeUserTypeSlots(PythonType/*!*/ type) {

            if (type.SlotCount == 0) {

                // if we later set the weak reference obj we'll create the array

                return null;

            }



            // weak reference is stored at end of slots

            object[] res = new object[type.SlotCount + 1];

            for (int i = 0; i < res.Length - 1; i++) {

                res[i] = Uninitialized.Instance;

            }

            return res;

        }



        public static bool IsClsVisible(CodeContext/*!*/ context) {

            return context.ModuleContext.ShowCls;

        }



        public static object GetInitMember(CodeContext/*!*/ context, PythonType type, object instance) {

            object value;

            bool res = type.TryGetNonCustomBoundMember(context, instance, "__init__", out value);

            Debug.Assert(res);



            return value;

        }



        public static object GetInitSlotMember(CodeContext/*!*/ context, PythonType type, PythonTypeSlot slot, object instance) {

            object value;

            if (!slot.TryGetValue(context, instance, type, out value)) {

                throw PythonOps.TypeError("bad __init__");

            }



            return value;

        }



        public static object GetMixedMember(CodeContext/*!*/ context, PythonType type, object instance, string name) {

            foreach (PythonType t in type.ResolutionOrder) {

                if (t.IsOldClass) {

                    OldClass oc = (OldClass)ToPythonType(t);

                    object ret;

                    if (oc._dict._storage.TryGetValue(name, out ret)) {

                        if (instance != null) return oc.GetOldStyleDescriptor(context, ret, instance, oc);

                        return ret;

                    }

                } else {

                    PythonTypeSlot dts;

                    if (t.TryLookupSlot(context, name, out dts)) {

                        object ret;

                        if (dts.TryGetValue(context, instance, type, out ret)) {

                            return ret;

                        }

                        return dts;

                    }

                }

            }



            throw AttributeErrorForMissingAttribute(type, name);

        }



        #region Slicing support



        /// <summary>

        /// Helper to determine if the value is a simple numeric type (int or big int or bool) - used for OldInstance

        /// deprecated form of slicing.

        /// </summary>

        public static bool IsNumericObject(object value) {

            return value is int || value is Extensible<int> || value is BigInteger || value is Extensible<BigInteger> || value is bool;

        }



        /// <summary>

        /// Helper to determine if the type is a simple numeric type (int or big int or bool) - used for OldInstance

        /// deprecated form of slicing.

        /// </summary>

        internal static bool IsNumericType(Type t) {

            return IsNonExtensibleNumericType(t) ||

                t.IsSubclassOf(typeof(Extensible<int>)) ||

                t.IsSubclassOf(typeof(Extensible<BigInteger>));

        }



        /// <summary>

        /// Helper to determine if the type is a simple numeric type (int or big int or bool) but not a subclass

        /// </summary>

        internal static bool IsNonExtensibleNumericType(Type t) {

            return t == typeof(int) ||

                t == typeof(bool) ||

                t == typeof(BigInteger);

        }



        /// <summary>

        /// For slicing.  Fixes up a BigInteger and returns an integer w/ the length of the

        /// object added if the value is negative.

        /// </summary>

        public static int NormalizeBigInteger(object self, BigInteger bi, ref Nullable<int> length) {

            int val;

            if (bi < BigInteger.Zero) {

                GetLengthOnce(self, ref length);



                if (bi.AsInt32(out val)) {

                    Debug.Assert(length.HasValue);

                    return val + length.Value;

                } else {

                    return -1;

                }

            } else if (bi.AsInt32(out val)) {

                return val;

            }



            return Int32.MaxValue;

        }



        /// <summary>

        /// For slicing.  Gets the length of the object, used to only get the length once.

        /// </summary>

        public static int GetLengthOnce(object self, ref Nullable<int> length) {

            if (length != null) return length.Value;



            length = PythonOps.Length(self);

            return length.Value;

        }



        #endregion



        public static ReflectedEvent.BoundEvent MakeBoundEvent(ReflectedEvent eventObj, object instance, Type type) {

            return new ReflectedEvent.BoundEvent(eventObj, instance, DynamicHelpers.GetPythonTypeFromType(type));

        }



        /// <summary>

        /// Helper method for DynamicSite rules that check the version of their dynamic object

        /// TODO - Remove this method for more direct field accesses

        /// </summary>

        /// <param name="o"></param>

        /// <param name="version"></param>

        /// <returns></returns>

        public static bool CheckTypeVersion(object o, int version) {

            IPythonObject po = o as IPythonObject;

            if (po == null) return false;



            return po.PythonType.Version == version;

        }



        public static bool CheckSpecificTypeVersion(PythonType type, int version) {

            return type.Version == version;

        }



        #region Conversion helpers



        internal static MethodInfo GetConversionHelper(string name, ConversionResultKind resultKind) {

            MethodInfo res;

            switch (resultKind) {

                case ConversionResultKind.ExplicitCast:

                case ConversionResultKind.ImplicitCast:

                    res = typeof(PythonOps).GetMethod("Throwing" + name);

                    break;

                case ConversionResultKind.ImplicitTry:

                case ConversionResultKind.ExplicitTry:

                    res = typeof(PythonOps).GetMethod("NonThrowing" + name);

                    break;

                default: throw new InvalidOperationException();

            }

            Debug.Assert(res != null);

            return res;

        }



        public static IEnumerable OldInstanceConvertToIEnumerableNonThrowing(CodeContext/*!*/ context, OldInstance/*!*/ self) {

            object callable;

            if (self.TryGetBoundCustomMember(context, "__iter__", out callable)) {

                return CreatePythonEnumerable(self);

            } else if (self.TryGetBoundCustomMember(context, "__getitem__", out callable)) {

                return CreateItemEnumerable(callable, PythonContext.GetContext(context).GetItemCallSite);

            }



            return null;

        }



        public static IEnumerable/*!*/ OldInstanceConvertToIEnumerableThrowing(CodeContext/*!*/ context, OldInstance/*!*/ self) {

            IEnumerable res = OldInstanceConvertToIEnumerableNonThrowing(context, self);

            if (res == null) {

                throw TypeErrorForTypeMismatch("IEnumerable", self);

            }



            return res;

        }



        public static IEnumerable<T> OldInstanceConvertToIEnumerableOfTNonThrowing<T>(CodeContext/*!*/ context, OldInstance/*!*/ self) {

            object callable;

            if (self.TryGetBoundCustomMember(context, "__iter__", out callable)) {

                return new IEnumerableOfTWrapper<T>(CreatePythonEnumerable(self));

            } else if (self.TryGetBoundCustomMember(context, "__getitem__", out callable)) {

                return new IEnumerableOfTWrapper<T>(CreateItemEnumerable(callable, PythonContext.GetContext(context).GetItemCallSite));

            }



            return null;

        }



        public static IEnumerable<T>/*!*/ OldInstanceConvertToIEnumerableOfTThrowing<T>(CodeContext/*!*/ context, OldInstance/*!*/ self) {

            IEnumerable<T> res = OldInstanceConvertToIEnumerableOfTNonThrowing<T>(context, self);

            if (res == null) {

                throw TypeErrorForTypeMismatch("IEnumerable[T]", self);

            }



            return res;

        }



        public static IEnumerator OldInstanceConvertToIEnumeratorNonThrowing(CodeContext/*!*/ context, OldInstance/*!*/ self) {

            object callable;

            if (self.TryGetBoundCustomMember(context, "__iter__", out callable)) {

                return CreatePythonEnumerator(self);

            } else if (self.TryGetBoundCustomMember(context, "__getitem__", out callable)) {

                return CreateItemEnumerator(callable, PythonContext.GetContext(context).GetItemCallSite);

            }



            return null;

        }



        public static IEnumerator/*!*/ OldInstanceConvertToIEnumeratorThrowing(CodeContext/*!*/ context, OldInstance/*!*/ self) {

            IEnumerator res = OldInstanceConvertToIEnumeratorNonThrowing(context, self);

            if (res == null) {

                throw TypeErrorForTypeMismatch("IEnumerator", self);

            }



            return res;

        }



        public static bool? OldInstanceConvertToBoolNonThrowing(CodeContext/*!*/ context, OldInstance/*!*/ oi) {

            object value;

            if (oi.TryGetBoundCustomMember(context, "__nonzero__", out value)) {

                object res = NonThrowingConvertToNonZero(PythonCalls.Call(context, value));

                if (res is int) {

                    return ((int)res) != 0;

                } else if (res is bool) {

                    return (bool)res;

                }

            } else if (oi.TryGetBoundCustomMember(context, "__len__", out value)) {

                int res;

                if (Converter.TryConvertToInt32(PythonCalls.Call(context, value), out res)) {

                    return res != 0;

                }

            }



            return null;

        }



        public static object OldInstanceConvertToBoolThrowing(CodeContext/*!*/ context, OldInstance/*!*/ oi) {

            object value;

            if (oi.TryGetBoundCustomMember(context, "__nonzero__", out value)) {

                return ThrowingConvertToNonZero(PythonCalls.Call(context, value));

            } else if (oi.TryGetBoundCustomMember(context, "__len__", out value)) {

                return PythonContext.GetContext(context).ConvertToInt32(PythonCalls.Call(context, value)) != 0;

            }



            return null;

        }



        public static object OldInstanceConvertNonThrowing(CodeContext/*!*/ context, OldInstance/*!*/ oi, string conversion) {

            object value;

            if (oi.TryGetBoundCustomMember(context, conversion, out value)) {

                if (conversion == "__int__") {

                    return NonThrowingConvertToInt(PythonCalls.Call(context, value));

                } else if (conversion == "__long__") {

                    return NonThrowingConvertToLong(PythonCalls.Call(context, value));

                } else if (conversion == "__float__") {

                    return NonThrowingConvertToFloat(PythonCalls.Call(context, value));

                } else if (conversion == "__complex__") {

                    return NonThrowingConvertToComplex(PythonCalls.Call(context, value));

                } else if (conversion == "__str__") {

                    return NonThrowingConvertToString(PythonCalls.Call(context, value));

                } else {

                    Debug.Assert(false);

                }

            } else if (conversion == "__complex__") {

                object res = OldInstanceConvertNonThrowing(context, oi, "__float__");

                if (res == null) {

                    return null;

                }



                return Converter.ConvertToComplex(res);

            }



            return null;

        }



        public static object OldInstanceConvertThrowing(CodeContext/*!*/ context, OldInstance/*!*/ oi, string conversion) {

            object value;

            if (oi.TryGetBoundCustomMember(context, conversion, out value)) {

                if (conversion == "__int__") {

                    return ThrowingConvertToInt(PythonCalls.Call(context, value));

                } else if (conversion == "__long__") {

                    return ThrowingConvertToLong(PythonCalls.Call(context, value));

                } else if (conversion == "__float__") {

                    return ThrowingConvertToFloat(PythonCalls.Call(context, value));

                } else if (conversion == "__complex__") {

                    return ThrowingConvertToComplex(PythonCalls.Call(context, value));

                } else if (conversion == "__str__") {

                    return ThrowingConvertToString(PythonCalls.Call(context, value));

                } else {

                    Debug.Assert(false);

                }

            } else if (conversion == "__complex__") {

                return OldInstanceConvertThrowing(context, oi, "__float__");

            }



            return null;

        }



        public static object ConvertFloatToComplex(object value) {

            if (value == null) {

                return null;

            }



            double d = (double)value;

            return new Complex(d, 0.0);

        }



        internal static bool CheckingConvertToInt(object value) {

            return value is int || value is BigInteger || value is Extensible<int> || value is Extensible<BigInteger>;

        }



        internal static bool CheckingConvertToLong(object value) {

            return CheckingConvertToInt(value);

        }



        internal static bool CheckingConvertToFloat(object value) {

            return value is double || (value != null && value is Extensible<double>);

        }



        internal static bool CheckingConvertToComplex(object value) {

            return value is Complex || value is Extensible<Complex> || CheckingConvertToInt(value) || CheckingConvertToFloat(value);

        }



        internal static bool CheckingConvertToString(object value) {

            return value is string || value is Extensible<string>;

        }



        public static bool CheckingConvertToNonZero(object value) {

            return value is bool || value is int;

        }



        public static object NonThrowingConvertToInt(object value) {

            if (!CheckingConvertToInt(value)) return null;

            return value;

        }



        public static object NonThrowingConvertToLong(object value) {

            if (!CheckingConvertToInt(value)) return null;

            return value;

        }



        public static object NonThrowingConvertToFloat(object value) {

            if (!CheckingConvertToFloat(value)) return null;

            return value;

        }



        public static object NonThrowingConvertToComplex(object value) {

            if (!CheckingConvertToComplex(value)) return null;

            return value;

        }



        public static object NonThrowingConvertToString(object value) {

            if (!CheckingConvertToString(value)) return null;

            return value;

        }



        public static object NonThrowingConvertToNonZero(object value) {

            if (!CheckingConvertToNonZero(value)) return null;

            return value;

        }



        public static object ThrowingConvertToInt(object value) {

            if (!CheckingConvertToInt(value)) throw TypeError(" __int__ returned non-int (type {0})", PythonTypeOps.GetName(value));

            return value;

        }



        public static object ThrowingConvertToFloat(object value) {

            if (!CheckingConvertToFloat(value)) throw TypeError(" __float__ returned non-float (type {0})", PythonTypeOps.GetName(value));

            return value;

        }



        public static object ThrowingConvertToComplex(object value) {

            if (!CheckingConvertToComplex(value)) throw TypeError(" __complex__ returned non-complex (type {0})", PythonTypeOps.GetName(value));

            return value;

        }



        public static object ThrowingConvertToLong(object value) {

            if (!CheckingConvertToComplex(value)) throw TypeError(" __long__ returned non-long (type {0})", PythonTypeOps.GetName(value));

            return value;

        }



        public static object ThrowingConvertToString(object value) {

            if (!CheckingConvertToString(value)) throw TypeError(" __str__ returned non-str (type {0})", PythonTypeOps.GetName(value));

            return value;

        }



        public static bool ThrowingConvertToNonZero(object value) {

            if (!CheckingConvertToNonZero(value)) throw TypeError("__nonzero__ should return bool or int, returned {0}", PythonTypeOps.GetName(value));

            if (value is bool) {

                return (bool)value;

            }



            return ((int)value) != 0;

        }



        #endregion



        public static bool SlotTryGetBoundValue(CodeContext/*!*/ context, PythonTypeSlot/*!*/ slot, object instance, PythonType owner, out object value) {

            Debug.Assert(slot != null);

            return slot.TryGetValue(context, instance, owner, out value);

        }



        public static bool SlotTryGetValue(CodeContext/*!*/ context, PythonTypeSlot/*!*/ slot, object instance, PythonType owner, out object value) {

            return slot.TryGetValue(context, instance, owner, out value);

        }



        public static object SlotGetValue(CodeContext/*!*/ context, PythonTypeSlot/*!*/ slot, object instance, PythonType owner) {

            object value;

            if (!slot.TryGetValue(context, instance, owner, out value)) {

                throw new InvalidOperationException();

            }



            return value;

        }



        public static bool SlotTrySetValue(CodeContext/*!*/ context, PythonTypeSlot/*!*/ slot, object instance, PythonType owner, object value) {

            return slot.TrySetValue(context, instance, owner, value);

        }



        public static object SlotSetValue(CodeContext/*!*/ context, PythonTypeSlot/*!*/ slot, object instance, PythonType owner, object value) {

            if (!slot.TrySetValue(context, instance, owner, value)) {

                throw new InvalidOperationException();

            }



            return value;

        }



        public static bool SlotTryDeleteValue(CodeContext/*!*/ context, PythonTypeSlot/*!*/ slot, object instance, PythonType owner) {

            return slot.TryDeleteValue(context, instance, owner);

        }



        public static BuiltinFunction/*!*/ MakeBoundBuiltinFunction(BuiltinFunction/*!*/ function, object/*!*/ target) {

            return function.BindToInstance(target);

        }



        public static object GetBuiltinFunctionSelf(BuiltinFunction function) {

            return function.BindingSelf;

        }



        /// <summary>

        /// Called from generated code.  Gets a builtin function and the BuiltinFunctionData associated

        /// with the object.  Tests to see if the function is bound and has the same data for the generated

        /// rule.

        /// </summary>

        public static bool TestBoundBuiltinFunction(BuiltinFunction/*!*/ function, object data) {

            if (function.IsUnbound) {

                // not bound

                return false;

            }



            return function.TestData(data);

        }



        public static BuiltinFunction/*!*/ GetBuiltinMethodDescriptorTemplate(BuiltinMethodDescriptor/*!*/ descriptor) {

            return descriptor.Template;

        }



        public static int GetTypeVersion(PythonType type) {

            return type.Version;

        }



        public static bool TryResolveTypeSlot(CodeContext/*!*/ context, PythonType type, string name, out PythonTypeSlot slot) {

            return type.TryResolveSlot(context, name, out slot);

        }



        public static T[] ConvertTupleToArray<T>(PythonTuple tuple) {

            T[] res = new T[tuple.__len__()];

            for (int i = 0; i < tuple.__len__(); i++) {

                try {

                    res[i] = (T)tuple[i];

                } catch (InvalidCastException) {

                    res[i] = Converter.Convert<T>(tuple[i]);

                }

            }

            return res;

        }



        #region Function helpers



        public static PythonGenerator MakeGenerator(PythonFunction function, MutableTuple data, object generatorCode) {

            Func<MutableTuple, object> next = generatorCode as Func<MutableTuple, object>;

            if (next == null) {

                next = ((LazyCode<Func<MutableTuple, object>>)generatorCode).EnsureDelegate();

            }



            return new PythonGenerator(function, next, data);

        }



        public static object MakeGeneratorExpression(object function, object input) {

            PythonFunction func = (PythonFunction)function;

            return ((Func<PythonFunction, object, object>)func.func_code.Target)(func, input);

        }



        public static FunctionCode MakeFunctionCode(CodeContext/*!*/ context, string name, string documentation, string[] argNames, FunctionAttributes flags, int startIndex, int endIndex, string path, Delegate code, string[] freeVars, string[] names, string[] cellVars, string[] varNames, int localCount) {

            Compiler.Ast.SerializedScopeStatement scope = new Compiler.Ast.SerializedScopeStatement(name, argNames, flags, startIndex, endIndex, path, freeVars, names, cellVars, varNames);



            return new FunctionCode(context.LanguageContext, code, scope, documentation, localCount);

        }



        [NoSideEffects]

        public static object MakeFunction(CodeContext/*!*/ context, FunctionCode funcInfo, object modName, object[] defaults) {

            return new PythonFunction(context, funcInfo, modName, defaults, null);

        }



        [NoSideEffects]

        public static object MakeFunctionDebug(CodeContext/*!*/ context, FunctionCode funcInfo, object modName, object[] defaults, Delegate target) {

            funcInfo.SetDebugTarget(PythonContext.GetContext(context), target);



            return new PythonFunction(context, funcInfo, modName, defaults, null);

        }



        public static CodeContext FunctionGetContext(PythonFunction func) {

            return func.Context;

        }



        public static object FunctionGetDefaultValue(PythonFunction func, int index) {

            return func.Defaults[index];

        }



        public static int FunctionGetCompatibility(PythonFunction func) {

            return func.FunctionCompatibility;

        }



        public static int FunctionGetID(PythonFunction func) {

            return func.FunctionID;

        }



        public static Delegate FunctionGetTarget(PythonFunction func) {

            return func.func_code.Target;

        }



        public static Delegate FunctionGetLightThrowTarget(PythonFunction func) {

            return func.func_code.LightThrowTarget;

        }



        public static void FunctionPushFrame(PythonContext context) {

            if (PythonFunction.AddRecursionDepth(1) > context.RecursionLimit) {

                throw PythonOps.RuntimeError("maximum recursion depth exceeded");

            }

        }



        public static void FunctionPushFrameCodeContext(CodeContext context) {

            FunctionPushFrame(PythonContext.GetContext(context));

        }



        public static void FunctionPopFrame() {

            PythonFunction.AddRecursionDepth(-1);

        }



        #endregion



        public static object ReturnConversionResult(object value) {

            PythonTuple pt = value as PythonTuple;

            if (pt != null) {

                return pt[0];

            }

            return NotImplementedType.Value;

        }



        /// <summary>

        /// Convert object to a given type. This code is equivalent to NewTypeMaker.EmitConvertFromObject

        /// except that it happens at runtime instead of compile time.

        /// </summary>

        public static T ConvertFromObject<T>(object obj) {

            Type toType = typeof(T);

            object result;

            MethodInfo fastConvertMethod = PythonBinder.GetFastConvertMethod(toType);

            if (fastConvertMethod != null) {

                result = fastConvertMethod.Invoke(null, new object[] { obj });

            } else if (typeof(Delegate).IsAssignableFrom(toType)) {

                result = Converter.ConvertToDelegate(obj, toType);

            } else {

                result = obj;

            }

            return (T)obj;

        }



        public static DynamicMetaObjectBinder MakeComplexCallAction(int count, bool list, string[] keywords) {

            Argument[] infos = CompilerHelpers.MakeRepeatedArray(Argument.Simple, count + keywords.Length);

            if (list) {

                infos[checked(count - 1)] = new Argument(ArgumentType.List);

            }

            for (int i = 0; i < keywords.Length; i++) {

                infos[count + i] = new Argument(keywords[i]);

            }



            return DefaultContext.DefaultPythonContext.Invoke(

                new CallSignature(infos)

            );

        }



        public static DynamicMetaObjectBinder MakeSimpleCallAction(int count) {

            return DefaultContext.DefaultPythonContext.Invoke(

                new CallSignature(CompilerHelpers.MakeRepeatedArray(Argument.Simple, count))

            );

        }



        public static PythonTuple ValidateCoerceResult(object coerceResult) {

            if (coerceResult == null || coerceResult == NotImplementedType.Value) {

                return null;

            }



            PythonTuple pt = coerceResult as PythonTuple;

            if (pt == null) throw PythonOps.TypeError("coercion should return None, NotImplemented, or 2-tuple, got {0}", PythonTypeOps.GetName(coerceResult));

            return pt;

        }



        public static object GetCoerceResultOne(PythonTuple coerceResult) {

            return coerceResult._data[0];

        }



        public static object GetCoerceResultTwo(PythonTuple coerceResult) {

            return coerceResult._data[1];

        }



        public static object MethodCheckSelf(CodeContext/*!*/ context, Method method, object self) {

            return method.CheckSelf(context, self);

        }



        [LightThrowing]

        public static object GeneratorCheckThrowableAndReturnSendValue(object self) {

            return ((PythonGenerator)self).CheckThrowableAndReturnSendValue();

        }



        public static ItemEnumerable CreateItemEnumerable(object callable, CallSite<Func<CallSite, CodeContext, object, int, object>> site) {

            return new ItemEnumerable(callable, site);

        }



        public static DictionaryKeyEnumerator MakeDictionaryKeyEnumerator(PythonDictionary dict) {

            return new DictionaryKeyEnumerator(dict._storage);

        }



        public static IEnumerable CreatePythonEnumerable(object baseObject) {

            return PythonEnumerable.Create(baseObject);

        }



        public static IEnumerator CreateItemEnumerator(object callable, CallSite<Func<CallSite, CodeContext, object, int, object>> site) {

            return new ItemEnumerator(callable, site);

        }



        public static IEnumerator CreatePythonEnumerator(object baseObject) {

            return PythonEnumerator.Create(baseObject);

        }



        public static bool ContainsFromEnumerable(CodeContext/*!*/ context, object enumerable, object value) {

            IEnumerator ie = enumerable as IEnumerator;

            if (ie == null) {

                IEnumerable ienum = enumerable as IEnumerable;

                if (ienum != null) {

                    ie = ienum.GetEnumerator();

                } else {

                    ie = Converter.ConvertToIEnumerator(enumerable);

                }

            }

            

            while (ie.MoveNext()) {

                if (PythonOps.EqualRetBool(context, ie.Current, value)) {

                    return true;

                }

            }

            return false;

        }



        public static object PythonTypeGetMember(CodeContext/*!*/ context, PythonType type, object instance, string name) {

            return type.GetMember(context, instance, name);

        }



        [NoSideEffects]

        public static object CheckUninitialized(object value, string name) {

            if (value == Uninitialized.Instance) {

                throw new UnboundLocalException(String.Format("Local variable '{0}' referenced before assignment.", name));

            }

            return value;

        }



        #region OldClass/OldInstance public helpers



        public static PythonDictionary OldClassGetDictionary(OldClass klass) {

            return klass._dict;

        }



        public static string OldClassGetName(OldClass klass) {

            return klass.Name;

        }



        public static bool OldInstanceIsCallable(CodeContext/*!*/ context, OldInstance/*!*/ self) {

            object dummy;

            return self.TryGetBoundCustomMember(context, "__call__", out dummy);

        }



        public static object OldClassCheckCallError(OldClass/*!*/ self, object dictionary, object list) {

            if ((dictionary != null && PythonOps.Length(dictionary) != 0) ||

                (list != null && PythonOps.Length(list) != 0)) {

                return OldClass.MakeCallError();

            }



            return null;

        }



        public static object OldClassSetBases(OldClass oc, object value) {

            oc.SetBases(value);

            return value;

        }



        public static object OldClassSetName(OldClass oc, object value) {

            oc.SetName(value);

            return value;

        }



        public static object OldClassSetDictionary(OldClass oc, object value) {

            oc.SetDictionary(value);

            return value;

        }



        public static object OldClassSetNameHelper(OldClass oc, string name, object value) {

            oc.SetNameHelper(name, value);

            return value;

        }



        public static object OldClassTryLookupInit(OldClass oc, object inst) {

            object ret;

            if (oc.TryLookupInit(inst, out ret)) {

                return ret;

            }

            return OperationFailed.Value;

        }



        public static object OldClassMakeCallError(OldClass oc) {

            return OldClass.MakeCallError();

        }



        public static PythonTuple OldClassGetBaseClasses(OldClass oc) {

            return PythonTuple.MakeTuple(oc.BaseClasses.ToArray());

        }



        public static void OldClassDictionaryIsPublic(OldClass oc) {

            oc.DictionaryIsPublic();

        }



        public static object OldClassTryLookupValue(CodeContext/*!*/ context, OldClass oc, string name) {

            object value;

            if (oc.TryLookupValue(context, name, out value)) {

                return value;

            }

            return OperationFailed.Value;

        }



        public static object OldClassLookupValue(CodeContext/*!*/ context, OldClass oc, string name) {

            return oc.LookupValue(context, name);

        }



        public static object OldInstanceGetOptimizedDictionary(OldInstance instance, int keyVersion) {

            CustomInstanceDictionaryStorage storage = instance.Dictionary._storage as CustomInstanceDictionaryStorage;

            if (storage == null || instance._class.HasSetAttr || storage.KeyVersion != keyVersion) {

                return null;

            }



            return storage;

        }



        public static object OldInstanceDictionaryGetValueHelper(object dict, int index, object oldInstance) {

            return ((CustomInstanceDictionaryStorage)dict).GetValueHelper(index, oldInstance);

        }



        public static bool TryOldInstanceDictionaryGetValueHelper(object dict, int index, object oldInstance, out object res) {

            return ((CustomInstanceDictionaryStorage)dict).TryGetValueHelper(index, oldInstance, out res);

        }



        public static object OldInstanceGetBoundMember(CodeContext/*!*/ context, OldInstance instance, string name) {

            return instance.GetBoundMember(context, name);

        }



        public static object OldInstanceDictionarySetExtraValue(object dict, int index, object value) {

            ((CustomInstanceDictionaryStorage)dict).SetExtraValue(index, value);

            return value;

        }



        public static object OldClassDeleteMember(CodeContext/*!*/ context, OldClass self, string name) {

            self.DeleteCustomMember(context, name);

            return null;

        }



        public static bool OldClassTryLookupOneSlot(PythonType type, OldClass self, string name, out object value) {

            return self.TryLookupOneSlot(type, name, out value);

        }



        public static object OldInstanceTryGetBoundCustomMember(CodeContext/*!*/ context, OldInstance self, string name) {

            object value;

            if (self.TryGetBoundCustomMember(context, name, out value)) {

                return value;

            }

            return OperationFailed.Value;

        }



        public static object OldInstanceSetCustomMember(CodeContext/*!*/ context, OldInstance self, string name, object value) {

            self.SetCustomMember(context, name, value);

            return value;

        }



        public static object OldInstanceDeleteCustomMember(CodeContext/*!*/ context, OldInstance self, string name) {

            self.DeleteCustomMember(context, name);

            return null;

        }



        #endregion



        public static object PythonTypeSetCustomMember(CodeContext/*!*/ context, PythonType self, string name, object value) {

            self.SetCustomMember(context, name, value);

            return value;

        }



        public static object PythonTypeDeleteCustomMember(CodeContext/*!*/ context, PythonType self, string name) {

            self.DeleteCustomMember(context, name);

            return null;

        }



        public static bool IsPythonType(PythonType type) {

            return type.IsPythonType;

        }



        public static object PublishModule(CodeContext/*!*/ context, string name) {

            object original = null;

            context.LanguageContext.SystemStateModules.TryGetValue(name, out original);

            var module = ((PythonScopeExtension)context.GlobalScope.GetExtension(context.LanguageContext.ContextId)).Module;

            context.LanguageContext.SystemStateModules[name] = module;

            return original;

        }



        public static void RemoveModule(CodeContext/*!*/ context, string name, object oldValue) {

            if (oldValue != null) {

                PythonContext.GetContext(context).SystemStateModules[name] = oldValue;

            } else {

                PythonContext.GetContext(context).SystemStateModules.Remove(name);

            }

        }



        public static Ellipsis Ellipsis {

            get {

                return Ellipsis.Value;

            }

        }



        public static NotImplementedType NotImplemented {

            get {

                return NotImplementedType.Value;

            }

        }



        public static void ListAddForComprehension(List l, object o) {

            l.AddNoLock(o);

        }



        public static void SetAddForComprehension(SetCollection s, object o) {

            s._items.AddNoLock(o);

        }



        public static void DictAddForComprehension(PythonDictionary d, object k, object v) {

            d._storage.AddNoLock(ref d._storage, k, v);

        }





        public static void ModuleStarted(CodeContext/*!*/ context, ModuleOptions features) {

            context.ModuleContext.Features |= features;

        }



        public static void Warn(CodeContext/*!*/ context, PythonType category, string message, params object[] args) {

            PythonContext pc = PythonContext.GetContext(context);

            object warnings = pc.GetWarningsModule(), warn = null;



            if (warnings != null) {

                warn = PythonOps.GetBoundAttr(context, warnings, "warn");

            }



            message = FormatWarning(message, args);



            if (warn == null) {

                PythonOps.PrintWithDest(context, pc.SystemStandardError, "warning: " + category.Name + ": " + message);

            } else {

                PythonOps.CallWithContext(context, warn, message, category);

            }

        }



        public static void ShowWarning(CodeContext/*!*/ context, PythonType category, string message, string filename, int lineNo) {

            PythonContext pc = PythonContext.GetContext(context);

            object warnings = pc.GetWarningsModule(), warn = null;



            if (warnings != null) {

                warn = PythonOps.GetBoundAttr(context, warnings, "showwarning");

            }



            if (warn == null) {

                PythonOps.PrintWithDestNoNewline(context, pc.SystemStandardError, String.Format("{0}:{1}: {2}: {3}\n", filename, lineNo, category.Name, message));

            } else {

                PythonOps.CallWithContext(context, warn, message, category, filename ?? "", lineNo);

            }

        }



        private static string FormatWarning(string message, object[] args) {

            for (int i = 0; i < args.Length; i++) {

                args[i] = PythonOps.ToString(args[i]);

            }



            message = String.Format(message, args);

            return message;

        }



        private static bool IsPrimitiveNumber(object o) {

            return IsNumericObject(o) ||

                o is Complex ||

                o is double ||

                o is Extensible<Complex> ||

                o is Extensible<double>;

        }



        public static void WarnDivision(CodeContext/*!*/ context, PythonDivisionOptions options, object self, object other) {

            if (options == PythonDivisionOptions.WarnAll) {

                if (IsPrimitiveNumber(self) && IsPrimitiveNumber(other)) {

                    if (self is Complex || other is Complex || self is Extensible<Complex> || other is Extensible<Complex>) {

                        Warn(context, PythonExceptions.DeprecationWarning, "classic complex division");

                        return;

                    } else if (self is double || other is double || self is Extensible<double> || other is Extensible<double>) {

                        Warn(context, PythonExceptions.DeprecationWarning, "classic float division");

                        return;

                    } else {

                        WarnDivisionInts(context, self, other);

                    }

                }

            } else if (IsNumericObject(self) && IsNumericObject(other)) {

                WarnDivisionInts(context, self, other);

            }

        }



        private static void WarnDivisionInts(CodeContext/*!*/ context, object self, object other) {

            if (self is BigInteger || other is BigInteger || self is Extensible<BigInteger> || other is Extensible<BigInteger>) {

                Warn(context, PythonExceptions.DeprecationWarning, "classic long division");

            } else {

                Warn(context, PythonExceptions.DeprecationWarning, "classic int division");

            }

        }



        public static DynamicMetaObjectBinder MakeComboAction(CodeContext/*!*/ context, DynamicMetaObjectBinder opBinder, DynamicMetaObjectBinder convBinder) {

            return PythonContext.GetContext(context).BinaryOperationRetType((PythonBinaryOperationBinder)opBinder, (PythonConversionBinder)convBinder);

        }



        public static DynamicMetaObjectBinder MakeInvokeAction(CodeContext/*!*/ context, CallSignature signature) {

            return PythonContext.GetContext(context).Invoke(signature);

        }



        public static DynamicMetaObjectBinder MakeGetAction(CodeContext/*!*/ context, string name, bool isNoThrow) {

            return PythonContext.GetContext(context).GetMember(name);

        }



        public static DynamicMetaObjectBinder MakeCompatGetAction(CodeContext/*!*/ context, string name) {

            return PythonContext.GetContext(context).CompatGetMember(name, false);

        }



        public static DynamicMetaObjectBinder MakeCompatInvokeAction(CodeContext/*!*/ context, CallInfo callInfo) {

            return PythonContext.GetContext(context).CompatInvoke(callInfo);

        }



        public static DynamicMetaObjectBinder MakeCompatConvertAction(CodeContext/*!*/ context, Type toType, bool isExplicit) {

            return PythonContext.GetContext(context).Convert(toType, isExplicit ? ConversionResultKind.ExplicitCast : ConversionResultKind.ImplicitCast).CompatBinder;

        }



        public static DynamicMetaObjectBinder MakeSetAction(CodeContext/*!*/ context, string name) {

            return PythonContext.GetContext(context).SetMember(name);

        }



        public static DynamicMetaObjectBinder MakeDeleteAction(CodeContext/*!*/ context, string name) {

            return PythonContext.GetContext(context).DeleteMember(name);

        }



        public static DynamicMetaObjectBinder MakeConversionAction(CodeContext/*!*/ context, Type type, ConversionResultKind kind) {

            return PythonContext.GetContext(context).Convert(type, kind);

        }



        public static DynamicMetaObjectBinder MakeTryConversionAction(CodeContext/*!*/ context, Type type, ConversionResultKind kind) {

            return PythonContext.GetContext(context).Convert(type, kind);

        }



        public static DynamicMetaObjectBinder MakeOperationAction(CodeContext/*!*/ context, int operationName) {

            return PythonContext.GetContext(context).Operation((PythonOperationKind)operationName);

        }



        public static DynamicMetaObjectBinder MakeUnaryOperationAction(CodeContext/*!*/ context, ExpressionType expressionType) {

            return PythonContext.GetContext(context).UnaryOperation(expressionType);

        }



        public static DynamicMetaObjectBinder MakeBinaryOperationAction(CodeContext/*!*/ context, ExpressionType expressionType) {

            return PythonContext.GetContext(context).BinaryOperation(expressionType);

        }



        public static DynamicMetaObjectBinder MakeGetIndexAction(CodeContext/*!*/ context, int argCount) {

            return PythonContext.GetContext(context).GetIndex(argCount);

        }



        public static DynamicMetaObjectBinder MakeSetIndexAction(CodeContext/*!*/ context, int argCount) {

            return PythonContext.GetContext(context).SetIndex(argCount);

        }



        public static DynamicMetaObjectBinder MakeDeleteIndexAction(CodeContext/*!*/ context, int argCount) {

            return PythonContext.GetContext(context).DeleteIndex(argCount);

        }



        public static DynamicMetaObjectBinder MakeGetSliceBinder(CodeContext/*!*/ context) {

            return PythonContext.GetContext(context).GetSlice;

        }



        public static DynamicMetaObjectBinder MakeSetSliceBinder(CodeContext/*!*/ context) {

            return PythonContext.GetContext(context).SetSliceBinder;

        }



        public static DynamicMetaObjectBinder MakeDeleteSliceBinder(CodeContext/*!*/ context) {

            return PythonContext.GetContext(context).DeleteSlice;

        }



        /// <summary>

        /// Provides access to AppDomain.DefineDynamicAssembly which cannot be called from a DynamicMethod

        /// </summary>

        public static AssemblyBuilder DefineDynamicAssembly(AssemblyName name, AssemblyBuilderAccess access) {

            return AppDomain.CurrentDomain.DefineDynamicAssembly(name, access);

        }



        /// <summary>

        /// Generates a new delegate type.  The last type in the array is the return type.

        /// </summary>

        public static Type/*!*/ MakeNewCustomDelegate(Type/*!*/[]/*!*/ types) {

            return MakeNewCustomDelegate(types, null);

        }



        /// <summary>

        /// Generates a new delegate type.  The last type in the array is the return type.

        /// </summary>

        public static Type/*!*/ MakeNewCustomDelegate(Type/*!*/[]/*!*/ types, CallingConvention? callingConvention) {

            const MethodAttributes CtorAttributes = MethodAttributes.RTSpecialName | MethodAttributes.HideBySig | MethodAttributes.Public;

            const MethodImplAttributes ImplAttributes = MethodImplAttributes.Runtime | MethodImplAttributes.Managed;

            const MethodAttributes InvokeAttributes = MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.NewSlot | MethodAttributes.Virtual;



            Type returnType = types[types.Length - 1];

            Type[] parameters = ArrayUtils.RemoveLast(types);



            TypeBuilder builder = Snippets.Shared.DefineDelegateType("Delegate" + types.Length);

            builder.DefineConstructor(CtorAttributes, CallingConventions.Standard, _DelegateCtorSignature).SetImplementationFlags(ImplAttributes);

            builder.DefineMethod("Invoke", InvokeAttributes, returnType, parameters).SetImplementationFlags(ImplAttributes);



            if (callingConvention != null) {

                builder.SetCustomAttribute(new CustomAttributeBuilder(

                    typeof(UnmanagedFunctionPointerAttribute).GetConstructor(new[] { typeof(CallingConvention) }),

                    new object[] { callingConvention })

                );

            }



            return builder.CreateType();

        }



#if !SILVERLIGHT

        /// <summary>

        /// Provides the entry point for a compiled module.  The stub exe calls into InitializeModule which

        /// does the actual work of adding references and importing the main module.  Upon completion it returns

        /// the exit code that the program reported via SystemExit or 0.

        /// </summary>

        public static int InitializeModule(Assembly/*!*/ precompiled, string/*!*/ main, string[] references) {

            ContractUtils.RequiresNotNull(precompiled, "precompiled");

            ContractUtils.RequiresNotNull(main, "main");



            Dictionary<string, object> options = new Dictionary<string, object>();

            options["Arguments"] = ArrayUtils.RemoveFirst(Environment.GetCommandLineArgs()); // remove the EXE



            var pythonEngine = Python.CreateEngine(options);



            var pythonContext = (PythonContext)HostingHelpers.GetLanguageContext(pythonEngine);





            foreach (var scriptCode in SavableScriptCode.LoadFromAssembly(pythonContext.DomainManager, precompiled)) {

                pythonContext.GetCompiledLoader().AddScriptCode(scriptCode);

            }



            if (references != null) {

                foreach (string referenceName in references) {

                    pythonContext.DomainManager.LoadAssembly(Assembly.Load(referenceName));

                }

            }



            ModuleContext modCtx = new ModuleContext(new PythonDictionary(), pythonContext);

            // import __main__

            try {

                Importer.Import(modCtx.GlobalContext, main, PythonTuple.EMPTY, 0);

            } catch (SystemExitException ex) {

                object dummy;

                return ex.GetExitCode(out dummy);

            }



            return 0;

        }

#endif



        public static CodeContext GetPythonTypeContext(PythonType pt) {

            return pt.PythonContext.SharedContext;

        }



        public static Delegate GetDelegate(CodeContext/*!*/ context, object target, Type type) {

            return context.LanguageContext.DelegateCreator.GetDelegate(target, type);

        }



        public static int CompareLists(List self, List other) {

            return self.CompareTo(other);

        }



        public static int CompareTuples(PythonTuple self, PythonTuple other) {

            return self.CompareTo(other);

        }



        public static int CompareFloats(double self, double other) {

            return DoubleOps.Compare(self, other);

        }



        public static Bytes MakeBytes(byte[] bytes) {

            return new Bytes(bytes);

        }



        public static byte[] MakeByteArray(this string s) {

            byte[] ret = new byte[s.Length];

            for (int i = 0; i < s.Length; i++) {

                if (s[i] < 0x100) ret[i] = (byte)s[i];

                else throw PythonOps.UnicodeEncodeError("'ascii' codec can't decode byte {0:X} in position {1}: ordinal not in range", (int)ret[i], i);

            }

            return ret;

        }



        public static string MakeString(this IList<byte> bytes) {

            return MakeString(bytes, bytes.Count);

        }



        internal static string MakeString(this byte[] preamble, IList<byte> bytes) {

            char[] chars = new char[preamble.Length + bytes.Count];

            for (int i = 0; i < preamble.Length; i++) {

                chars[i] = (char)preamble[i];

            }

            for (int i = 0; i < bytes.Count; i++) {

                chars[i + preamble.Length] = (char)bytes[i];

            }

            return new String(chars);

        }



        internal static string MakeString(this IList<byte> bytes, int maxBytes) {

            int bytesToCopy = Math.Min(bytes.Count, maxBytes);

            StringBuilder b = new StringBuilder(bytesToCopy);

            for (int i = 0; i < bytesToCopy; i++) {

                b.Append((char)bytes[i]);

            }

            return b.ToString();

        }



        /// <summary>

        /// Called from generated code, helper to remove a name

        /// </summary>

        public static void RemoveName(CodeContext/*!*/ context, string name) {

            if (!context.TryRemoveVariable(name)) {

                throw PythonOps.NameError(name);

            }

        }



        /// <summary>

        /// Called from generated code, helper to do name lookup

        /// </summary>

        public static object LookupName(CodeContext/*!*/ context, string name) {

            object value;

            if (context.TryLookupName(name, out value)) {

                return value;

            } else if (context.TryLookupBuiltin(name, out value)) {

                return value;

            }



            throw PythonOps.NameError(name);

        }



        /// <summary>

        /// Called from generated code, helper to do name assignment

        /// </summary>

        public static object SetName(CodeContext/*!*/ context, string name, object value) {

            context.SetVariable(name, value);

            return value;

        }



        /// <summary>

        /// Returns an IntPtr in the proper way to CPython - an int or a Python long

        /// </summary>

        public static object/*!*/ ToPython(this IntPtr handle) {

            long value = handle.ToInt64();

            if (value >= Int32.MinValue && value <= Int32.MaxValue) {

                return ScriptingRuntimeHelpers.Int32ToObject((int)value);

            }



            return (BigInteger)value;

        }



        #region Global Access



        public static CodeContext/*!*/ CreateLocalContext(CodeContext/*!*/ outerContext, MutableTuple boxes, string[] args) {

            return new CodeContext(

                new PythonDictionary(

                    new RuntimeVariablesDictionaryStorage(boxes, args)

                ),

                outerContext.ModuleContext

            );

        }



        public static CodeContext/*!*/ GetGlobalContext(CodeContext/*!*/ context) {

            return context.ModuleContext.GlobalContext;

        }



        public static ClosureCell/*!*/ MakeClosureCell() {

            return new ClosureCell(Uninitialized.Instance);

        }



        public static ClosureCell/*!*/ MakeClosureCellWithValue(object initialValue) {

            return new ClosureCell(initialValue);

        }



        public static MutableTuple/*!*/ GetClosureTupleFromFunction(PythonFunction/*!*/ function) {

            return GetClosureTupleFromContext(function.Context);

        }



        public static MutableTuple/*!*/ GetClosureTupleFromGenerator(PythonGenerator/*!*/ generator) {

            return GetClosureTupleFromContext(generator.Context);

        }



        public static MutableTuple/*!*/ GetClosureTupleFromContext(CodeContext/*!*/ context) {

            return (context.Dict._storage as RuntimeVariablesDictionaryStorage).Tuple;

        }



        public static CodeContext/*!*/ GetParentContextFromFunction(PythonFunction/*!*/ function) {

            return function.Context;

        }



        public static CodeContext/*!*/ GetParentContextFromGenerator(PythonGenerator/*!*/ generator) {

            return generator.Context;

        }



        public static object GetGlobal(CodeContext/*!*/ context, string name) {

            return GetVariable(context, name, true, false);

        }



        public static object GetLocal(CodeContext/*!*/ context, string name) {

            return GetVariable(context, name, false, false);

        }



        internal static object GetVariable(CodeContext/*!*/ context, string name, bool isGlobal, bool lightThrow) {

            object res;

            if (isGlobal) {

                if (context.TryGetGlobalVariable(name, out res)) {

                    return res;

                }

            } else {

                if (context.TryLookupName(name, out res)) {

                    return res;

                }

            }



            PythonDictionary builtins = context.GetBuiltinsDict();

            if (builtins != null && builtins.TryGetValue(name, out res)) {

                return res;

            }



            Exception ex;

            if (isGlobal) {

                ex = GlobalNameError(name);

            } else {

                ex = NameError(name);

            }

            if (lightThrow) {

                return LightExceptions.Throw(ex);

            }

            throw ex;

        }



        public static object RawGetGlobal(CodeContext/*!*/ context, string name) {

            object res;

            if (context.TryGetGlobalVariable(name, out res)) {

                return res;

            }



            return Uninitialized.Instance;

        }



        public static object RawGetLocal(CodeContext/*!*/ context, string name) {

            object res;

            if (context.TryLookupName(name, out res)) {

                return res;

            }



            return Uninitialized.Instance;

        }



        public static void SetGlobal(CodeContext/*!*/ context, string name, object value) {

            context.SetGlobalVariable(name, value);

        }



        public static void SetLocal(CodeContext/*!*/ context, string name, object value) {

            context.SetVariable(name, value);

        }



        public static void DeleteGlobal(CodeContext/*!*/ context, string name) {

            if (context.TryRemoveGlobalVariable(name)) {

                return;

            }



            throw NameError(name);

        }



        public static void DeleteLocal(CodeContext/*!*/ context, string name) {

            if (context.TryRemoveVariable(name)) {

                return;

            }



            throw NameError(name);

        }



        public static PythonGlobal/*!*/[] GetGlobalArrayFromContext(CodeContext/*!*/ context) {

            return context.GetGlobalArray();

        }



        #endregion



        #region Exception Factories



        public static Exception MultipleKeywordArgumentError(PythonFunction function, string name) {

            return TypeError("{0}() got multiple values for keyword argument '{1}'", function.__name__, name);

        }



        public static Exception UnexpectedKeywordArgumentError(PythonFunction function, string name) {

            return TypeError("{0}() got an unexpected keyword argument '{1}'", function.__name__, name);

        }



        public static Exception StaticAssignmentFromInstanceError(PropertyTracker tracker, bool isAssignment) {

            if (isAssignment) {

                if (DynamicHelpers.GetPythonTypeFromType(tracker.DeclaringType).IsPythonType) {

                    return PythonOps.TypeError(

                        "can't set attributes of built-in/extension type '{0}'",

                        NameConverter.GetTypeName(tracker.DeclaringType));

                }



                return new MissingMemberException(string.Format(

                    Resources.StaticAssignmentFromInstanceError,

                    tracker.Name,

                    NameConverter.GetTypeName(tracker.DeclaringType)));

            }

            return new MissingMemberException(string.Format(Resources.StaticAccessFromInstanceError,

                tracker.Name,

                NameConverter.GetTypeName(tracker.DeclaringType)));

        }



        public static Exception FunctionBadArgumentError(PythonFunction func, int count) {

            return func.BadArgumentError(count);

        }



        public static Exception BadKeywordArgumentError(PythonFunction func, int count) {

            return func.BadKeywordArgumentError(count);

        }



        public static Exception AttributeErrorForMissingOrReadonly(CodeContext/*!*/ context, PythonType dt, string name) {

            PythonTypeSlot dts;

            if (dt.TryResolveSlot(context, name, out dts)) {

                throw PythonOps.AttributeErrorForReadonlyAttribute(dt.Name, name);

            }



            throw PythonOps.AttributeErrorForMissingAttribute(dt.Name, name);

        }



        public static Exception AttributeErrorForMissingAttribute(object o, string name) {

            PythonType dt = o as PythonType;

            if (dt != null)

                return PythonOps.AttributeErrorForMissingAttribute(dt.Name, name);



            return AttributeErrorForReadonlyAttribute(PythonTypeOps.GetName(o), name);

        }





        public static Exception ValueError(string format, params object[] args) {

            return new ValueErrorException(string.Format(format, args));

        }



        public static Exception KeyError(object key) {

            return PythonExceptions.CreateThrowable(PythonExceptions.KeyError, key);

        }



        public static Exception KeyError(string format, params object[] args) {

            return new KeyNotFoundException(string.Format(format, args));

        }



        public static Exception UnicodeDecodeError(string format, params object[] args) {

            return new System.Text.DecoderFallbackException(string.Format(format, args));

        }



        public static Exception UnicodeEncodeError(string format, params object[] args) {

            return new System.Text.EncoderFallbackException(string.Format(format, args));

        }



        public static Exception IOError(Exception inner) {

            return new System.IO.IOException(inner.Message, inner);

        }



        public static Exception IOError(string format, params object[] args) {

            return new System.IO.IOException(string.Format(format, args));

        }



        public static Exception EofError(string format, params object[] args) {

            return new System.IO.EndOfStreamException(string.Format(format, args));

        }



        public static Exception StandardError(string format, params object[] args) {

            return new SystemException(string.Format(format, args));

        }



        public static Exception ZeroDivisionError(string format, params object[] args) {

            return new DivideByZeroException(string.Format(format, args));

        }



        public static Exception SystemError(string format, params object[] args) {

            return new SystemException(string.Format(format, args));

        }



        public static Exception TypeError(string format, params object[] args) {

            return new TypeErrorException(string.Format(format, args));

        }



        public static Exception IndexError(string format, params object[] args) {

            return new System.IndexOutOfRangeException(string.Format(format, args));

        }



        public static Exception MemoryError(string format, params object[] args) {

            return new OutOfMemoryException(string.Format(format, args));

        }



        public static Exception ArithmeticError(string format, params object[] args) {

            return new ArithmeticException(string.Format(format, args));

        }



        public static Exception NotImplementedError(string format, params object[] args) {

            return new NotImplementedException(string.Format(format, args));

        }



        public static Exception AttributeError(string format, params object[] args) {

            return new MissingMemberException(string.Format(format, args));

        }



        public static Exception OverflowError(string format, params object[] args) {

            return new System.OverflowException(string.Format(format, args));

        }

        public static Exception WindowsError(string format, params object[] args) {

#if !SILVERLIGHT // System.ComponentModel.Win32Exception

            return new System.ComponentModel.Win32Exception(string.Format(format, args));

#else

            return new System.SystemException(string.Format(format, args));

#endif

        }



        public static Exception SystemExit() {

            return new SystemExitException();

        }



        public static void SyntaxWarning(string message, SourceUnit sourceUnit, SourceSpan span, int errorCode) {

            PythonContext pc = (PythonContext)sourceUnit.LanguageContext;

            CodeContext context = pc.SharedContext;



            ShowWarning(context, PythonExceptions.SyntaxWarning, message, sourceUnit.Path, span.Start.Line);

        }



        public static SyntaxErrorException SyntaxError(string message, SourceUnit sourceUnit, SourceSpan span, int errorCode) {

            switch (errorCode & ErrorCodes.ErrorMask) {

                case ErrorCodes.IndentationError:

                    return new IndentationException(message, sourceUnit, span, errorCode, Severity.FatalError);



                case ErrorCodes.TabError:

                    return new TabException(message, sourceUnit, span, errorCode, Severity.FatalError);



                default:

                    var res = new SyntaxErrorException(message, sourceUnit, span, errorCode, Severity.FatalError);

                    if ((errorCode & ErrorCodes.NoCaret) != 0) {

                        res.Data[PythonContext._syntaxErrorNoCaret] = ScriptingRuntimeHelpers.True;

                    }

                    return res;

            }

        }



        public static SyntaxErrorException BadSourceError(byte badByte, SourceSpan span, string path) {

            SyntaxErrorException res = new SyntaxErrorException(

                String.Format("Non-ASCII character '\\x{0:x2}' in file {2} on line {1}, but no encoding declared; see http://www.python.org/peps/pep-0263.html for details",

                    badByte,

                    span.Start.Line,

                    path

                ),

                path,

                null,

                null,

                span,

                ErrorCodes.SyntaxError,

                Severity.FatalError

            );

            res.Data[PythonContext._syntaxErrorNoCaret] = ScriptingRuntimeHelpers.True;

            return res;

        }



        public static Exception StopIteration() {

            return StopIteration("");

        }



        public static Exception InvalidType(object o, RuntimeTypeHandle handle) {

            return PythonOps.TypeErrorForTypeMismatch(DynamicHelpers.GetPythonTypeFromType(Type.GetTypeFromHandle(handle)).Name, o);

        }



        public static Exception ZeroDivisionError() {

            return ZeroDivisionError("Attempted to divide by zero.");

        }



        // If you do "(a, b) = (1, 2, 3, 4)"

        public static Exception ValueErrorForUnpackMismatch(int left, int right) {

            System.Diagnostics.Debug.Assert(left != right);



            if (left > right)

                return ValueError("need more than {0} values to unpack", right);

            else

                return ValueError("too many values to unpack");

        }



        public static Exception NameError(string name) {

            return new UnboundNameException(string.Format("name '{0}' is not defined", name));

        }



        public static Exception GlobalNameError(string name) {

            return new UnboundNameException(string.Format("global name '{0}' is not defined", name));

        }



        // If an unbound method is called without a "self" argument, or a "self" argument of a bad type

        public static Exception TypeErrorForUnboundMethodCall(string methodName, Type methodType, object instance) {

            return TypeErrorForUnboundMethodCall(methodName, DynamicHelpers.GetPythonTypeFromType(methodType), instance);

        }



        public static Exception TypeErrorForUnboundMethodCall(string methodName, PythonType methodType, object instance) {

            string message = string.Format("unbound method {0}() must be called with {1} instance as first argument (got {2} instead)",

                                           methodName, methodType.Name, PythonTypeOps.GetName(instance));

            return TypeError(message);

        }



        // When a generator first starts, before it gets to the first yield point, you can't call generator.Send(x) where x != null.

        // See Pep342 for details.

        public static Exception TypeErrorForIllegalSend() {

            string message = "can't send non-None value to a just-started generator";

            return TypeError(message);

        }



        // If a method is called with an incorrect number of arguments

        // You should use TypeErrorForUnboundMethodCall() for unbound methods called with 0 arguments

        public static Exception TypeErrorForArgumentCountMismatch(string methodName, int expectedArgCount, int actualArgCount) {

            return TypeError("{0}() takes exactly {1} argument{2} ({3} given)",

                             methodName, expectedArgCount, expectedArgCount == 1 ? "" : "s", actualArgCount);

        }



        public static Exception TypeErrorForTypeMismatch(string expectedTypeName, object instance) {

            return TypeError("expected {0}, got {1}", expectedTypeName, PythonOps.GetPythonTypeName(instance));

        }



        // If hash is called on an instance of an unhashable type

        public static Exception TypeErrorForUnhashableType(string typeName) {

            return TypeError(typeName + " objects are unhashable");

        }



        public static Exception TypeErrorForUnhashableObject(object obj) {

            return TypeErrorForUnhashableType(PythonTypeOps.GetName(obj));

        }



        internal static Exception TypeErrorForIncompatibleObjectLayout(string prefix, PythonType type, Type newType) {

            return TypeError("{0}: '{1}' object layout differs from '{2}'", prefix, type.Name, newType);

        }



        public static Exception TypeErrorForNonStringAttribute() {

            return TypeError("attribute name must be string");

        }



        internal static Exception TypeErrorForBadInstance(string template, object instance) {

            return TypeError(template, PythonOps.GetPythonTypeName(instance));

        }



        public static Exception TypeErrorForBinaryOp(string opSymbol, object x, object y) {

            throw PythonOps.TypeError("unsupported operand type(s) for {0}: '{1}' and '{2}'",

                                opSymbol, GetPythonTypeName(x), GetPythonTypeName(y));

        }



        public static Exception TypeErrorForUnaryOp(string opSymbol, object x) {

            throw PythonOps.TypeError("unsupported operand type for {0}: '{1}'",

                                opSymbol, GetPythonTypeName(x));

        }



        public static Exception TypeErrorForNonIterableObject(object o) {

            return PythonOps.TypeError(

                "argument of type '{0}' is not iterable",

                PythonTypeOps.GetName(o)

            );

        }



        public static Exception TypeErrorForDefaultArgument(string message) {

            return PythonOps.TypeError(message);

        }



        public static Exception AttributeErrorForReadonlyAttribute(string typeName, string attributeName) {

            // CPython uses AttributeError for all attributes except "__class__"

            if (attributeName == "__class__")

                return PythonOps.TypeError("can't delete __class__ attribute");



            return PythonOps.AttributeError("attribute '{0}' of '{1}' object is read-only", attributeName, typeName);

        }



        public static Exception AttributeErrorForBuiltinAttributeDeletion(string typeName, string attributeName) {

            return PythonOps.AttributeError("cannot delete attribute '{0}' of builtin type '{1}'", attributeName, typeName);

        }



        public static Exception MissingInvokeMethodException(object o, string name) {

            if (o is OldClass) {

                throw PythonOps.AttributeError("type object '{0}' has no attribute '{1}'",

                    ((OldClass)o).Name, name);

            } else {

                throw PythonOps.AttributeError("'{0}' object has no attribute '{1}'", GetPythonTypeName(o), name);

            }

        }



        /// <summary>

        /// Create at TypeError exception for when Raise() can't create the exception requested.  

        /// </summary>

        /// <param name="type">original type of exception requested</param>

        /// <returns>a TypeEror exception</returns>

        internal static Exception MakeExceptionTypeError(object type) {

            return PythonOps.TypeError("exceptions must be classes, or instances, not {0}", PythonTypeOps.GetName(type));

        }



        public static Exception AttributeErrorForObjectMissingAttribute(object obj, string attributeName) {

            if (obj is OldInstance) {

                return AttributeErrorForOldInstanceMissingAttribute(((OldInstance)obj)._class.Name, attributeName);

            } else if (obj is OldClass) {

                return AttributeErrorForOldClassMissingAttribute(((OldClass)obj).Name, attributeName);

            } else {

                return AttributeErrorForMissingAttribute(PythonTypeOps.GetName(obj), attributeName);

            }

        }



        public static Exception AttributeErrorForMissingAttribute(string typeName, string attributeName) {

            return PythonOps.AttributeError("'{0}' object has no attribute '{1}'", typeName, attributeName);

        }



        public static Exception AttributeErrorForOldInstanceMissingAttribute(string typeName, string attributeName) {

            return PythonOps.AttributeError("{0} instance has no attribute '{1}'", typeName, attributeName);

        }



        public static Exception AttributeErrorForOldClassMissingAttribute(string typeName, string attributeName) {

            return PythonOps.AttributeError("class {0} has no attribute '{1}'", typeName, attributeName);

        }



        public static Exception UncallableError(object func) {

            return PythonOps.TypeError("{0} is not callable", PythonTypeOps.GetName(func));

        }



        public static Exception TypeErrorForProtectedMember(Type/*!*/ type, string/*!*/ name) {

            return PythonOps.TypeError("cannot access protected member {0} without a python subclass of {1}", name, NameConverter.GetTypeName(type));

        }



        public static Exception TypeErrorForGenericMethod(Type/*!*/ type, string/*!*/ name) {

            return PythonOps.TypeError("{0}.{1} is a generic method and must be indexed with types before calling", NameConverter.GetTypeName(type), name);

        }



        public static Exception TypeErrorForUnIndexableObject(object o) {

            IPythonObject ipo;

            if (o == null) {

                return PythonOps.TypeError("'NoneType' object cannot be interpreted as an index");

            } else if ((ipo = o as IPythonObject) != null) {

                return TypeError("'{0}' object cannot be interpreted as an index", ipo.PythonType.Name);

            }



            return TypeError("object cannot be interpreted as an index");

        }



        [Obsolete("no longer used anywhere")]

        public static Exception/*!*/ TypeErrorForBadDictionaryArgument(PythonFunction/*!*/ f) {

            return PythonOps.TypeError("{0}() argument after ** must be a dictionary", f.__name__);

        }



        public static T TypeErrorForBadEnumConversion<T>(object value) {

            throw TypeError("Cannot convert numeric value {0} to {1}.  The value must be zero.", value, NameConverter.GetTypeName(typeof(T)));

        }



        public static Exception/*!*/ UnreadableProperty() {

            return PythonOps.AttributeError("unreadable attribute");

        }





        public static Exception/*!*/ UnsetableProperty() {

            return PythonOps.AttributeError("readonly attribute");

        }



        public static Exception/*!*/ UndeletableProperty() {

            return PythonOps.AttributeError("undeletable attribute");

        }



        public static Exception Warning(string format, params object[] args) {

            return new WarningException(string.Format(format, args));

        }



        #endregion



        [ThreadStatic]

        private static List<FunctionStack> _funcStack;



        public static List<FunctionStack> GetFunctionStack() {

            return _funcStack ?? (_funcStack = new List<FunctionStack>());

        }



        public static List<FunctionStack> GetFunctionStackNoCreate() {

            return _funcStack;

        }



        public static List<FunctionStack> PushFrame(CodeContext/*!*/ context, FunctionCode function) {

            List<FunctionStack> stack = GetFunctionStack();

            stack.Add(new FunctionStack(context, function));

            return stack;

        }



        internal static LightLambdaExpression ToGenerator(this LightLambdaExpression code, bool shouldInterpret, bool debuggable, int compilationThreshold) {

            return Utils.LightLambda(

                typeof(object),

                code.Type,

                new GeneratorRewriter(code.Name, code.Body).Reduce(shouldInterpret, debuggable, compilationThreshold, code.Parameters, x => x),

                code.Name,

                code.Parameters

            );

        }



        public static void UpdateStackTrace(Exception e, CodeContext context, FunctionCode funcCode, int line) {

            if (line != -1) {

                Debug.Assert(line != SourceLocation.None.Line);



                List<DynamicStackFrame> pyFrames = e.GetFrameList();

                

                if (pyFrames == null) {

                    e.SetFrameList(pyFrames = new List<DynamicStackFrame>());

                }



                var frame = new PythonDynamicStackFrame(context, funcCode, line);

                funcCode.LightThrowCompile(context);

                pyFrames.Add(frame);

            }

        }



        /// <summary>

        /// Gets a list of DynamicStackFrames for the given exception.  These stack frames

        /// can be programmatically inspected to understand the frames the exception crossed

        /// through including Python frames.

        /// 

        /// Dynamic stack frames are not preserved when an exception crosses an app domain

        /// boundary.

        /// </summary>

        public static DynamicStackFrame[] GetDynamicStackFrames(Exception e) {

            return PythonExceptions.GetDynamicStackFrames(e);

        }



        public static byte[] ConvertBufferToByteArray(PythonBuffer buffer) {

            return buffer.ToString().MakeByteArray();

        }



        public static bool ModuleTryGetMember(CodeContext/*!*/ context, PythonModule module, string name, out object res) {

            object value = module.GetAttributeNoThrow(context, name);

            if (value != OperationFailed.Value) {

                res = value;

                return true;

            }



            res = null;

            return false;

        }



        internal static void ScopeSetMember(CodeContext/*!*/ context, Scope scope, string name, object value) {

            ScopeStorage scopeStorage = ((object)scope.Storage) as ScopeStorage;

            if (scopeStorage != null) {

                scopeStorage.SetValue(name, false, value);

                return;

            }



            PythonOps.SetAttr(context, scope, name, value);

        }



        internal static object ScopeGetMember(CodeContext/*!*/ context, Scope scope, string name) {

            ScopeStorage scopeStorage = ((object)scope.Storage) as ScopeStorage;

            if (scopeStorage != null) {

                return scopeStorage.GetValue(name, false);

            }



            return PythonOps.GetBoundAttr(context, scope, name);

        }



        internal static bool ScopeTryGetMember(CodeContext/*!*/ context, Scope scope, string name, out object value) {

            ScopeStorage scopeStorage = ((object)scope.Storage) as ScopeStorage;

            if (scopeStorage != null) {

                return scopeStorage.TryGetValue(name, false, out value);

            }



            return PythonOps.TryGetBoundAttr(context, scope, name, out value);

        }



        internal static bool ScopeContainsMember(CodeContext/*!*/ context, Scope scope, string name) {

            ScopeStorage scopeStorage = ((object)scope.Storage) as ScopeStorage;

            if (scopeStorage != null) {

                return scopeStorage.HasValue(name, false);

            }



            return PythonOps.HasAttr(context, scope, name);

        }



        internal static bool ScopeDeleteMember(CodeContext/*!*/ context, Scope scope, string name) {

            ScopeStorage scopeStorage = ((object)scope.Storage) as ScopeStorage;

            if (scopeStorage != null) {

                return scopeStorage.DeleteValue(name, false);

            }



            bool res = PythonOps.HasAttr(context, scope, name);

            PythonOps.DeleteAttr(context, scope, name);

            return res;

        }



        internal static IList<object> ScopeGetMemberNames(CodeContext/*!*/ context, Scope scope) {

            ScopeStorage scopeStorage = ((object)scope.Storage) as ScopeStorage;

            if (scopeStorage != null) {

                List<object> res = new List<object>();



                foreach (string name in scopeStorage.GetMemberNames()) {

                    res.Add(name);

                }



                var objKeys = ((PythonScopeExtension)context.LanguageContext.EnsureScopeExtension(scope)).ObjectKeys;

                if (objKeys != null) {

                    foreach (object o in objKeys.Keys) {

                        res.Add(o);

                    }

                }



                return res;

            }



            return PythonOps.GetAttrNames(context, scope);

        }



        public static bool IsUnicode(object unicodeObj) {

            return unicodeObj == TypeCache.String;

        }



        public static BuiltinFunction GetUnicodeFuntion() {

            return UnicodeHelper.Function;

        }



        public static bool IsExtensionSet(CodeContext codeContext, int id) {

            return codeContext.ModuleContext.ExtensionMethods.Id == id;

        }



        public static object GetExtensionMethodSet(CodeContext context) {

            return context.ModuleContext.ExtensionMethods;

        }

    }



    /// <summary>

    /// Helper clas for calls to unicode(...).  We generate code which checks if unicode

    /// is str and if it is we redirect those calls to the unicode function defined on this

    /// class.

    /// </summary>

    public class UnicodeHelper {

        internal static BuiltinFunction Function = BuiltinFunction.MakeFunction("unicode",

            ArrayUtils.ConvertAll(

                typeof(UnicodeHelper).GetMember("unicode"),

                x => (MethodInfo)x

            ),

            typeof(string)

        );



        public static object unicode(CodeContext context) {

            return String.Empty;

        }



        public static object unicode(CodeContext/*!*/ context, object @string) {

            return StringOps.FastNewUnicode(context, @string);

        }



        public static object unicode(CodeContext/*!*/ context, object @string, object encoding) {

            return StringOps.FastNewUnicode(context, @string, encoding);

        }



        public static object unicode(CodeContext/*!*/ context, object @string, [Optional]object encoding, object errors) {

            return StringOps.FastNewUnicode(context, @string, encoding, errors);

        }

    }



    public struct FunctionStack {

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes")]

        public readonly CodeContext/*!*/ Context;

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes")]

        public readonly FunctionCode/*!*/ Code;

        public TraceBackFrame Frame;



        internal FunctionStack(CodeContext/*!*/ context, FunctionCode/*!*/ code) {

            Assert.NotNull(context, code);



            Context = context;

            Code = code;

            Frame = null;

        }



        internal FunctionStack(CodeContext/*!*/ context, FunctionCode/*!*/ code, TraceBackFrame frame) {

            Assert.NotNull(context, code);



            Context = context;

            Code = code;

            Frame = frame;

        }



        internal FunctionStack(TraceBackFrame frame) {

            Context = frame.Context;

            Code = frame.f_code;

            Frame = frame;

        }

    }



}