/SampleParsers/Program.cs

// ----------------------------------------------------------------------------------------------

// Copyright (c) Mårten Rånge.

// ----------------------------------------------------------------------------------------------

// This source code is subject to terms and conditions of the Microsoft Public License. A 

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

// If you cannot locate the  Microsoft Public License, 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 Microsoft Public License.

// ----------------------------------------------------------------------------------------------

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

// ----------------------------------------------------------------------------------------------

using System;

using System.Collections.Generic;

using System.Linq.Expressions;

using System.Reflection;

using MicroParser;



// ReSharper disable InconsistentNaming



namespace SampleParsers

{

   static class Program

   {

      static void Main (string[] args)

      {

         Sample1 ();



         Sample2 ();



         Console.ReadKey ();

      }



      static Program ()

      {

         // Sample1



         {

            // Int () is a builtin parser for ints

            var p_int = CharParser.Int ();



            var p_identifier = CharParser

               .ManyCharSatisfy2 (              // Creates a string parser

               CharSatisfy.Letter,              // A test function applied to the 

                                                // first character

               CharSatisfy.LetterOrDigit,       // A test function applied to the

                                                // rest of the characters

               minCount: 1                      // We require the identifier to be 

                                                // at least 1 character long

               );



            var p_spaces = CharParser.SkipWhiteSpace ();

            var p_assignment = CharParser.SkipChar ('=');



            s_parserSample1 = Parser.Group (

               p_identifier.KeepLeft (p_spaces),

               p_assignment.KeepRight (p_spaces).KeepRight (p_int));



         }



         // Sample2



         {

            // Define a parameter expression that represent a dictionary, this dictionary

            // will contain the variable values

            var inputParameter = Expression.Parameter (

               typeof (IDictionary<string, double>),

               "input"

               );



            Func<string, Parser<Empty>> p_str = CharParser.SkipString;



            var p_spaces = CharParser.SkipWhiteSpace ();

            // Parse a double and map it into a ConstantExpression

            var p_value = CharParser.Double ().Map (d => (Expression) Expression.Constant (d));

            var p_variable = CharParser

               .ManyCharSatisfy2 (

                  CharSatisfy.Letter,

                  CharSatisfy.LetterOrDigit,

                  minCount: 1

               )

               .Map (identifier => (Expression) Expression.Call (

                  null,

                  s_findVariableValueSample2,

                  inputParameter,

                  Expression.Constant (identifier.ToString ()))

               );



            var p_astRedirect = Parser.Redirect<Expression> ();



            // p_ast is the complete parser (AST = Abstract Syntax Tree)

            var p_ast = p_astRedirect.Parser;



            var p_term = Parser.Choice (

               p_ast.Between (p_str ("(").KeepLeft (p_spaces), p_str (")")),

               p_value,

               p_variable

               ).KeepLeft (p_spaces);



            // p_level is a support parser generator

            // it accepts a parser it will apply on the input separated by the operators

            // in the ops parameter

            Func<Parser<Expression>, string, Parser<Expression>> p_level =

               (parser, ops) => parser.Chain (

                  CharParser.AnyOf (ops, minCount:1, maxCount:1).KeepLeft (p_spaces),

                  (left, op, right) => 

                     Expression.MakeBinary (OperatorToExpressionType (op), left, right)

                  );



            // By splitting */ and +- like this we ensure */ binds _harder_

            var p_lvl0 = p_level (p_term, "*/");

            var p_lvl1 = p_level (p_lvl0, "+-");



            // This completes the parser

            p_astRedirect.ParserRedirect = p_lvl1;



            s_parameterSample2 = inputParameter;

            s_parserSample2 = p_ast;

         }

      }



      // Sample1



      static readonly Parser<Tuple<SubString, int>> s_parserSample1;



      static void Sample1 ()

      {



         var result = Parser.Parse (

            s_parserSample1,

            "AnIdentifier = 3"

            );



         if (result.IsSuccessful)

         {

            Console.WriteLine (

               "{0} = {1}", 

               result.Value.Item1, 

               result.Value.Item2

               );

         }

         else

         {

            Console.WriteLine (

               result.ErrorMessage 

               );

         }

      }





      // Sample2



      static readonly ParameterExpression s_parameterSample2;

      static readonly Parser<Expression> s_parserSample2;

      static readonly MethodInfo s_findVariableValueSample2 = GetMethodInfo (() => FindVariableValue (null, null));



      static MethodInfo GetMethodInfo (Expression<Action> expression)

      {

         return ((MethodCallExpression)expression.Body).Method;

      }



      static double FindVariableValue (IDictionary<string, double> input, string name)

      {

         double value;

         return input.TryGetValue (name ?? "", out value) ? value : 0.0;

      }





      static ExpressionType OperatorToExpressionType (SubString op)

      {

         switch (op[0])

         {

            case '+':

               return ExpressionType.Add;

            case '-':

               return ExpressionType.Subtract;

            case '*':

               return ExpressionType.Multiply;

            case '/':

               return ExpressionType.Divide;

            default:

               throw new ArgumentException ();

         }

      }



      static void Sample2 ()

      {



         var input = new Dictionary<string, double>

                        {

                           {"x", 1.0},

                           {"y", 2.0},

                        };



         var expression = "2*(x + 1) + y + 3";



         var result = Parser.Parse (s_parserSample2, expression);



         if (result.IsSuccessful)

         {

            var lambda = Expression.Lambda<Func<IDictionary<string, double>, double>> (

               result.Value,

               s_parameterSample2

               );



            var del = lambda.Compile ();



            Console.WriteLine ("{0} = {1}", expression, del (input));

            foreach (var kv in input)

            {

               Console.WriteLine ("{0} = {1}", kv.Key, kv.Value);

            }

         }

         else

         {

            Console.WriteLine (

               result.ErrorMessage

               );

         }





      }



   }

}