/*  parsermodule.c
 *
 *  Copyright 1995-1996 by Fred L. Drake, Jr. and Virginia Polytechnic
 *  Institute and State University, Blacksburg, Virginia, USA.
 *  Portions copyright 1991-1995 by Stichting Mathematisch Centrum,
 *  Amsterdam, The Netherlands.  Copying is permitted under the terms
 *  associated with the main Python distribution, with the additional
 *  restriction that this additional notice be included and maintained
 *  on all distributed copies.
 *
 *  This module serves to replace the original parser module written
 *  by Guido.  The functionality is not matched precisely, but the
 *  original may be implemented on top of this.  This is desirable
 *  since the source of the text to be parsed is now divorced from
 *  this interface.
 *
 *  Unlike the prior interface, the ability to give a parse tree
 *  produced by Python code as a tuple to the compiler is enabled by
 *  this module.  See the documentation for more details.
 *
 *  I've added some annotations that help with the lint code-checking
 *  program, but they're not complete by a long shot.  The real errors
 *  that lint detects are gone, but there are still warnings with
 *  Py_[X]DECREF() and Py_[X]INCREF() macros.  The lint annotations
 *  look like "NOTE(...)".
 */

#include "Python.h"                     /* general Python API             */
#include "Python-ast.h"                 /* mod_ty */
#include "graminit.h"                   /* symbols defined in the grammar */
#include "node.h"                       /* internal parser structure      */
#include "errcode.h"                    /* error codes for PyNode_*()     */
#include "token.h"                      /* token definitions              */
#include "grammar.h"
#include "parsetok.h"
                                        /* ISTERMINAL() / ISNONTERMINAL() */
#include "compile.h"
#undef Yield
#include "ast.h"
#include "pyarena.h"

extern grammar _PyParser_Grammar; /* From graminit.c */

#ifdef lint
#include <note.h>
#else
#define NOTE(x)
#endif

/*  String constants used to initialize module attributes.
 *
 */
static char parser_copyright_string[] =
"Copyright 1995-1996 by Virginia Polytechnic Institute & State\n\
University, Blacksburg, Virginia, USA, and Fred L. Drake, Jr., Reston,\n\
Virginia, USA.  Portions copyright 1991-1995 by Stichting Mathematisch\n\
Centrum, Amsterdam, The Netherlands.";


PyDoc_STRVAR(parser_doc_string,
"This is an interface to Python's internal parser.");

static char parser_version_string[] = "0.5";


typedef PyObject* (*SeqMaker) (Py_ssize_t length);
typedef int (*SeqInserter) (PyObject* sequence,
                            Py_ssize_t index,
                            PyObject* element);

/*  The function below is copyrighted by Stichting Mathematisch Centrum.  The
 *  original copyright statement is included below, and continues to apply
 *  in full to the function immediately following.  All other material is
 *  original, copyrighted by Fred L. Drake, Jr. and Virginia Polytechnic
 *  Institute and State University.  Changes were made to comply with the
 *  new naming conventions.  Added arguments to provide support for creating
 *  lists as well as tuples, and optionally including the line numbers.
 */


static PyObject*
node2tuple(node *n,                     /* node to convert               */
           SeqMaker mkseq,              /* create sequence               */
           SeqInserter addelem,         /* func. to add elem. in seq.    */
           int lineno,                  /* include line numbers?         */
           int col_offset)              /* include column offsets?       */
{
    if (n == NULL) {
        Py_INCREF(Py_None);
        return (Py_None);
    }
    if (ISNONTERMINAL(TYPE(n))) {
        int i;
        PyObject *v;
        PyObject *w;

        v = mkseq(1 + NCH(n) + (TYPE(n) == encoding_decl));
        if (v == NULL)
            return (v);
        w = PyInt_FromLong(TYPE(n));
        if (w == NULL) {
            Py_DECREF(v);
            return ((PyObject*) NULL);
        }
        (void) addelem(v, 0, w);
        for (i = 0; i < NCH(n); i++) {
            w = node2tuple(CHILD(n, i), mkseq, addelem, lineno, col_offset);
            if (w == NULL) {
                Py_DECREF(v);
                return ((PyObject*) NULL);
            }
            (void) addelem(v, i+1, w);
        }

        if (TYPE(n) == encoding_decl)
            (void) addelem(v, i+1, PyString_FromString(STR(n)));
        return (v);
    }
    else if (ISTERMINAL(TYPE(n))) {
        PyObject *result = mkseq(2 + lineno + col_offset);
        if (result != NULL) {
            (void) addelem(result, 0, PyInt_FromLong(TYPE(n)));
            (void) addelem(result, 1, PyString_FromString(STR(n)));
            if (lineno == 1)
                (void) addelem(result, 2, PyInt_FromLong(n->n_lineno));
            if (col_offset == 1)
                (void) addelem(result, 3, PyInt_FromLong(n->n_col_offset));
        }
        return (result);
    }
    else {
        PyErr_SetString(PyExc_SystemError,
                        "unrecognized parse tree node type");
        return ((PyObject*) NULL);
    }
}
/*
 *  End of material copyrighted by Stichting Mathematisch Centrum.
 */



/*  There are two types of intermediate objects we're interested in:
 *  'eval' and 'exec' types.  These constants can be used in the st_type
 *  field of the object type to identify which any given object represents.
 *  These should probably go in an external header to allow other extensions
 *  to use them, but then, we really should be using C++ too.  ;-)
 */

#define PyST_EXPR  1
#define PyST_SUITE 2


/*  These are the internal objects and definitions required to implement the
 *  ST type.  Most of the internal names are more reminiscent of the 'old'
 *  naming style, but the code uses the new naming convention.
 */

static PyObject*
parser_error = 0;


typedef struct {
    PyObject_HEAD                       /* standard object header           */
    node* st_node;                      /* the node* returned by the parser */
    int   st_type;                      /* EXPR or SUITE ?                  */
    PyCompilerFlags st_flags;           /* Parser and compiler flags        */
} PyST_Object;


static void parser_free(PyST_Object *st);
static int parser_compare(PyST_Object *left, PyST_Object *right);
static PyObject *parser_getattr(PyObject *self, char *name);


static
PyTypeObject PyST_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "parser.st",                        /* tp_name              */
    (int) sizeof(PyST_Object),          /* tp_basicsize         */
    0,                                  /* tp_itemsize          */
    (destructor)parser_free,            /* tp_dealloc           */
    0,                                  /* tp_print             */
    parser_getattr,                     /* tp_getattr           */
    0,                                  /* tp_setattr           */
    (cmpfunc)parser_compare,            /* tp_compare           */
    0,                                  /* tp_repr              */
    0,                                  /* tp_as_number         */
    0,                                  /* tp_as_sequence       */
    0,                                  /* tp_as_mapping        */
    0,                                  /* tp_hash              */
    0,                                  /* tp_call              */
    0,                                  /* tp_str               */
    0,                                  /* tp_getattro          */
    0,                                  /* tp_setattro          */

    /* Functions to access object as input/output buffer */
    0,                                  /* tp_as_buffer         */

    Py_TPFLAGS_DEFAULT,                 /* tp_flags             */

    /* __doc__ */
    "Intermediate representation of a Python parse tree."
};  /* PyST_Type */


static int
parser_compare_nodes(node *left, node *right)
{
    int j;

    if (TYPE(left) < TYPE(right))
        return (-1);

    if (TYPE(right) < TYPE(left))
        return (1);

    if (ISTERMINAL(TYPE(left)))
        return (strcmp(STR(left), STR(right)));

    if (NCH(left) < NCH(right))
        return (-1);

    if (NCH(right) < NCH(left))
        return (1);

    for (j = 0; j < NCH(left); ++j) {
        int v = parser_compare_nodes(CHILD(left, j), CHILD(right, j));

        if (v != 0)
            return (v);
    }
    return (0);
}


/*  int parser_compare(PyST_Object* left, PyST_Object* right)
 *
 *  Comparison function used by the Python operators ==, !=, <, >, <=, >=
 *  This really just wraps a call to parser_compare_nodes() with some easy
 *  checks and protection code.
 *
 */
static int
parser_compare(PyST_Object *left, PyST_Object *right)
{
    if (left == right)
        return (0);

    if ((left == 0) || (right == 0))
        return (-1);

    return (parser_compare_nodes(left->st_node, right->st_node));
}


/*  parser_newstobject(node* st)
 *
 *  Allocates a new Python object representing an ST.  This is simply the
 *  'wrapper' object that holds a node* and allows it to be passed around in
 *  Python code.
 *
 */
static PyObject*
parser_newstobject(node *st, int type)
{
    PyST_Object* o = PyObject_New(PyST_Object, &PyST_Type);

    if (o != 0) {
        o->st_node = st;
        o->st_type = type;
        o->st_flags.cf_flags = 0;
    }
    else {
        PyNode_Free(st);
    }
    return ((PyObject*)o);
}


/*  void parser_free(PyST_Object* st)
 *
 *  This is called by a del statement that reduces the reference count to 0.
 *
 */
static void
parser_free(PyST_Object *st)
{
    PyNode_Free(st->st_node);
    PyObject_Del(st);
}


/*  parser_st2tuple(PyObject* self, PyObject* args, PyObject* kw)
 *
 *  This provides conversion from a node* to a tuple object that can be
 *  returned to the Python-level caller.  The ST object is not modified.
 *
 */
static PyObject*
parser_st2tuple(PyST_Object *self, PyObject *args, PyObject *kw)
{
    PyObject *line_option = 0;
    PyObject *col_option = 0;
    PyObject *res = 0;
    int ok;

    static char *keywords[] = {"ast", "line_info", "col_info", NULL};

    if (self == NULL) {
        ok = PyArg_ParseTupleAndKeywords(args, kw, "O!|OO:st2tuple", keywords,
                                         &PyST_Type, &self, &line_option,
                                         &col_option);
    }
    else
        ok = PyArg_ParseTupleAndKeywords(args, kw, "|OO:totuple", &keywords[1],
                                         &line_option, &col_option);
    if (ok != 0) {
        int lineno = 0;
        int col_offset = 0;
        if (line_option != NULL) {
            lineno = (PyObject_IsTrue(line_option) != 0) ? 1 : 0;
        }
        if (col_option != NULL) {
            col_offset = (PyObject_IsTrue(col_option) != 0) ? 1 : 0;
        }
        /*
         *  Convert ST into a tuple representation.  Use Guido's function,
         *  since it's known to work already.
         */
        res = node2tuple(((PyST_Object*)self)->st_node,
                         PyTuple_New, PyTuple_SetItem, lineno, col_offset);
    }
    return (res);
}

static PyObject*
parser_ast2tuple(PyST_Object *self, PyObject *args, PyObject *kw)
{
    if (PyErr_WarnPy3k("ast2tuple is removed in 3.x; use st2tuple", 1) < 0)
        return NULL;
    return parser_st2tuple(self, args, kw);
}


/*  parser_st2list(PyObject* self, PyObject* args, PyObject* kw)
 *
 *  This provides conversion from a node* to a list object that can be
 *  returned to the Python-level caller.  The ST object is not modified.
 *
 */
static PyObject*
parser_st2list(PyST_Object *self, PyObject *args, PyObject *kw)
{
    PyObject *line_option = 0;
    PyObject *col_option = 0;
    PyObject *res = 0;
    int ok;

    static char *keywords[] = {"ast", "line_info", "col_info", NULL};

    if (self == NULL)
        ok = PyArg_ParseTupleAndKeywords(args, kw, "O!|OO:st2list", keywords,
                                         &PyST_Type, &self, &line_option,
                                         &col_option);
    else
        ok = PyArg_ParseTupleAndKeywords(args, kw, "|OO:tolist", &keywords[1],
                                         &line_option, &col_option);
    if (ok) {
        int lineno = 0;
        int col_offset = 0;
        if (line_option != 0) {
            lineno = PyObject_IsTrue(line_option) ? 1 : 0;
        }
        if (col_option != NULL) {
            col_offset = (PyObject_IsTrue(col_option) != 0) ? 1 : 0;
        }
        /*
         *  Convert ST into a tuple representation.  Use Guido's function,
         *  since it's known to work already.
         */
        res = node2tuple(self->st_node,
                         PyList_New, PyList_SetItem, lineno, col_offset);
    }
    return (res);
}

static PyObject*
parser_ast2list(PyST_Object *self, PyObject *args, PyObject *kw)
{
    if (PyErr_WarnPy3k("ast2list is removed in 3.x; use st2list", 1) < 0)
        return NULL;
    return parser_st2list(self, args, kw);
}


/*  parser_compilest(PyObject* self, PyObject* args)
 *
 *  This function creates code objects from the parse tree represented by
 *  the passed-in data object.  An optional file name is passed in as well.
 *
 */
static PyObject*
parser_compilest(PyST_Object *self, PyObject *args, PyObject *kw)
{
    PyObject*     res = 0;
    PyArena*      arena;
    mod_ty        mod;
    char*         str = "<syntax-tree>";
    int ok;

    static char *keywords[] = {"ast", "filename", NULL};

    if (self == NULL)
        ok = PyArg_ParseTupleAndKeywords(args, kw, "O!|s:compilest", keywords,
                                         &PyST_Type, &self, &str);
    else
        ok = PyArg_ParseTupleAndKeywords(args, kw, "|s:compile", &keywords[1],
                                         &str);

    if (ok) {
        arena = PyArena_New();
        if (arena) {
           mod = PyAST_FromNode(self->st_node, &(self->st_flags), str, arena);
           if (mod) {
               res = (PyObject *)PyAST_Compile(mod, str, &(self->st_flags), arena);
           }
           PyArena_Free(arena);
        }
    }

    return (res);
}

static PyObject*
parser_compileast(PyST_Object *self, PyObject *args, PyObject *kw)
{
    if (PyErr_WarnPy3k("compileast is removed in 3.x; use compilest", 1) < 0)
        return NULL;
    return parser_compilest(self, args, kw);
}


/*  PyObject* parser_isexpr(PyObject* self, PyObject* args)
 *  PyObject* parser_issuite(PyObject* self, PyObject* args)
 *
 *  Checks the passed-in ST object to determine if it is an expression or
 *  a statement suite, respectively.  The return is a Python truth value.
 *
 */
static PyObject*
parser_isexpr(PyST_Object *self, PyObject *args, PyObject *kw)
{
    PyObject* res = 0;
    int ok;

    static char *keywords[] = {"ast", NULL};

    if (self == NULL)
        ok = PyArg_ParseTupleAndKeywords(args, kw, "O!:isexpr", keywords,
                                         &PyST_Type, &self);
    else
        ok = PyArg_ParseTupleAndKeywords(args, kw, ":isexpr", &keywords[1]);

    if (ok) {
        /* Check to see if the ST represents an expression or not. */
        res = (self->st_type == PyST_EXPR) ? Py_True : Py_False;
        Py_INCREF(res);
    }
    return (res);
}


static PyObject*
parser_issuite(PyST_Object *self, PyObject *args, PyObject *kw)
{
    PyObject* res = 0;
    int ok;

    static char *keywords[] = {"ast", NULL};

    if (self == NULL)
        ok = PyArg_ParseTupleAndKeywords(args, kw, "O!:issuite", keywords,
                                         &PyST_Type, &self);
    else
        ok = PyArg_ParseTupleAndKeywords(args, kw, ":issuite", &keywords[1]);

    if (ok) {
        /* Check to see if the ST represents an expression or not. */
        res = (self->st_type == PyST_EXPR) ? Py_False : Py_True;
        Py_INCREF(res);
    }
    return (res);
}


#define PUBLIC_METHOD_TYPE (METH_VARARGS|METH_KEYWORDS)

static PyMethodDef
parser_methods[] = {
    {"compile",         (PyCFunction)parser_compilest,  PUBLIC_METHOD_TYPE,
        PyDoc_STR("Compile this ST object into a code object.")},
    {"isexpr",          (PyCFunction)parser_isexpr,     PUBLIC_METHOD_TYPE,
        PyDoc_STR("Determines if this ST object was created from an expression.")},
    {"issuite",         (PyCFunction)parser_issuite,    PUBLIC_METHOD_TYPE,
        PyDoc_STR("Determines if this ST object was created from a suite.")},
    {"tolist",          (PyCFunction)parser_st2list,    PUBLIC_METHOD_TYPE,
        PyDoc_STR("Creates a list-tree representation of this ST.")},
    {"totuple",         (PyCFunction)parser_st2tuple,   PUBLIC_METHOD_TYPE,
        PyDoc_STR("Creates a tuple-tree representation of this ST.")},

    {NULL, NULL, 0, NULL}
};


static PyObject*
parser_getattr(PyObject *self, char *name)
{
    return (Py_FindMethod(parser_methods, self, name));
}


/*  err_string(char* message)
 *
 *  Sets the error string for an exception of type ParserError.
 *
 */
static void
err_string(char *message)
{
    PyErr_SetString(parser_error, message);
}


/*  PyObject* parser_do_parse(PyObject* args, int type)
 *
 *  Internal function to actually execute the parse and return the result if
 *  successful or set an exception if not.
 *
 */
static PyObject*
parser_do_parse(PyObject *args, PyObject *kw, char *argspec, int type)
{
    char*     string = 0;
    PyObject* res    = 0;
    int flags        = 0;
    perrdetail err;

    static char *keywords[] = {"source", NULL};

    if (PyArg_ParseTupleAndKeywords(args, kw, argspec, keywords, &string)) {
        node* n = PyParser_ParseStringFlagsFilenameEx(string, NULL,
                                                       &_PyParser_Grammar,
                                                      (type == PyST_EXPR)
                                                      ? eval_input : file_input,
                                                      &err, &flags);

	if (n) {
	    res = parser_newstobject(n, type);
            if (res)
                ((PyST_Object *)res)->st_flags.cf_flags = flags & PyCF_MASK;
        }
        else
            PyParser_SetError(&err);
    }
    return (res);
}


/*  PyObject* parser_expr(PyObject* self, PyObject* args)
 *  PyObject* parser_suite(PyObject* self, PyObject* args)
 *
 *  External interfaces to the parser itself.  Which is called determines if
 *  the parser attempts to recognize an expression ('eval' form) or statement
 *  suite ('exec' form).  The real work is done by parser_do_parse() above.
 *
 */
static PyObject*
parser_expr(PyST_Object *self, PyObject *args, PyObject *kw)
{
    NOTE(ARGUNUSED(self))
    return (parser_do_parse(args, kw, "s:expr", PyST_EXPR));
}


static PyObject*
parser_suite(PyST_Object *self, PyObject *args, PyObject *kw)
{
    NOTE(ARGUNUSED(self))
    return (parser_do_parse(args, kw, "s:suite", PyST_SUITE));
}



/*  This is the messy part of the code.  Conversion from a tuple to an ST
 *  object requires that the input tuple be valid without having to rely on
 *  catching an exception from the compiler.  This is done to allow the
 *  compiler itself to remain fast, since most of its input will come from
 *  the parser directly, and therefore be known to be syntactically correct.
 *  This validation is done to ensure that we don't core dump the compile
 *  phase, returning an exception instead.
 *
 *  Two aspects can be broken out in this code:  creating a node tree from
 *  the tuple passed in, and verifying that it is indeed valid.  It may be
 *  advantageous to expand the number of ST types to include funcdefs and
 *  lambdadefs to take advantage of the optimizer, recognizing those STs
 *  here.  They are not necessary, and not quite as useful in a raw form.
 *  For now, let's get expressions and suites working reliably.
 */


static node* build_node_tree(PyObject *tuple);
static int   validate_expr_tree(node *tree);
static int   validate_file_input(node *tree);
static int   validate_encoding_decl(node *tree);

/*  PyObject* parser_tuple2st(PyObject* self, PyObject* args)
 *
 *  This is the public function, called from the Python code.  It receives a
 *  single tuple object from the caller, and creates an ST object if the
 *  tuple can be validated.  It does this by checking the first code of the
 *  tuple, and, if acceptable, builds the internal representation.  If this
 *  step succeeds, the internal representation is validated as fully as
 *  possible with the various validate_*() routines defined below.
 *
 *  This function must be changed if support is to be added for PyST_FRAGMENT
 *  ST objects.
 *
 */
static PyObject*
parser_tuple2st(PyST_Object *self, PyObject *args, PyObject *kw)
{
    NOTE(ARGUNUSED(self))
    PyObject *st = 0;
    PyObject *tuple;
    node *tree;

    static char *keywords[] = {"sequence", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, kw, "O:sequence2st", keywords,
                                     &tuple))
        return (0);
    if (!PySequence_Check(tuple)) {
        PyErr_SetString(PyExc_ValueError,
                        "sequence2st() requires a single sequence argument");
        return (0);
    }
    /*
     *  Convert the tree to the internal form before checking it.
     */
    tree = build_node_tree(tuple);
    if (tree != 0) {
        int start_sym = TYPE(tree);
        if (start_sym == eval_input) {
            /*  Might be an eval form.  */
            if (validate_expr_tree(tree))
                st = parser_newstobject(tree, PyST_EXPR);
            else
                PyNode_Free(tree);
        }
        else if (start_sym == file_input) {
            /*  This looks like an exec form so far.  */
            if (validate_file_input(tree))
                st = parser_newstobject(tree, PyST_SUITE);
            else
                PyNode_Free(tree);
        }
        else if (start_sym == encoding_decl) {
            /* This looks like an encoding_decl so far. */
            if (validate_encoding_decl(tree))
                st = parser_newstobject(tree, PyST_SUITE);
            else
                PyNode_Free(tree);
        }
        else {
            /*  This is a fragment, at best. */
            PyNode_Free(tree);
            err_string("parse tree does not use a valid start symbol");
        }
    }
    /*  Make sure we throw an exception on all errors.  We should never
     *  get this, but we'd do well to be sure something is done.
     */
    if (st == NULL && !PyErr_Occurred())
        err_string("unspecified ST error occurred");

    return st;
}

static PyObject*
parser_tuple2ast(PyST_Object *self, PyObject *args, PyObject *kw)
{
    if (PyErr_WarnPy3k("tuple2ast is removed in 3.x; use tuple2st", 1) < 0)
        return NULL;
    return parser_tuple2st(self, args, kw);
}


/*  node* build_node_children()
 *
 *  Iterate across the children of the current non-terminal node and build
 *  their structures.  If successful, return the root of this portion of
 *  the tree, otherwise, 0.  Any required exception will be specified already,
 *  and no memory will have been deallocated.
 *
 */
static node*
build_node_children(PyObject *tuple, node *root, int *line_num)
{
    Py_ssize_t len = PyObject_Size(tuple);
    Py_ssize_t i;
    int  err;

    for (i = 1; i < len; ++i) {
        /* elem must always be a sequence, however simple */
        PyObject* elem = PySequence_GetItem(tuple, i);
        int ok = elem != NULL;
        long  type = 0;
        char *strn = 0;

        if (ok)
            ok = PySequence_Check(elem);
        if (ok) {
            PyObject *temp = PySequence_GetItem(elem, 0);
            if (temp == NULL)
                ok = 0;
            else {
                ok = PyInt_Check(temp);
                if (ok)
                    type = PyInt_AS_LONG(temp);
                Py_DECREF(temp);
            }
        }
        if (!ok) {
            PyObject *err = Py_BuildValue("os", elem,
                                          "Illegal node construct.");
            PyErr_SetObject(parser_error, err);
            Py_XDECREF(err);
            Py_XDECREF(elem);
            return (0);
        }
        if (ISTERMINAL(type)) {
            Py_ssize_t len = PyObject_Size(elem);
            PyObject *temp;

            if ((len != 2) && (len != 3)) {
                err_string("terminal nodes must have 2 or 3 entries");
                return 0;
            }
            temp = PySequence_GetItem(elem, 1);
            if (temp == NULL)
                return 0;
            if (!PyString_Check(temp)) {
                PyErr_Format(parser_error,
                             "second item in terminal node must be a string,"
                             " found %s",
                             Py_TYPE(temp)->tp_name);
                Py_DECREF(temp);
                return 0;
            }
            if (len == 3) {
                PyObject *o = PySequence_GetItem(elem, 2);
                if (o != NULL) {
                    if (PyInt_Check(o))
                        *line_num = PyInt_AS_LONG(o);
                    else {
                        PyErr_Format(parser_error,
                                     "third item in terminal node must be an"
                                     " integer, found %s",
				     Py_TYPE(temp)->tp_name);
                        Py_DECREF(o);
                        Py_DECREF(temp);
                        return 0;
                    }
                    Py_DECREF(o);
                }
            }
            len = PyString_GET_SIZE(temp) + 1;
            strn = (char *)PyObject_MALLOC(len);
            if (strn != NULL)
                (void) memcpy(strn, PyString_AS_STRING(temp), len);
            Py_DECREF(temp);
        }
        else if (!ISNONTERMINAL(type)) {
            /*
             *  It has to be one or the other; this is an error.
             *  Throw an exception.
             */
            PyObject *err = Py_BuildValue("os", elem, "unknown node type.");
            PyErr_SetObject(parser_error, err);
            Py_XDECREF(err);
            Py_XDECREF(elem);
            return (0);
        }
        err = PyNode_AddChild(root, type, strn, *line_num, 0);
        if (err == E_NOMEM) {
            PyObject_FREE(strn);
            return (node *) PyErr_NoMemory();
        }
        if (err == E_OVERFLOW) {
            PyObject_FREE(strn);
            PyErr_SetString(PyExc_ValueError,
                            "unsupported number of child nodes");
            return NULL;
        }

        if (ISNONTERMINAL(type)) {
            node* new_child = CHILD(root, i - 1);

            if (new_child != build_node_children(elem, new_child, line_num)) {
                Py_XDECREF(elem);
                return (0);
            }
        }
        else if (type == NEWLINE) {     /* It's true:  we increment the     */
            ++(*line_num);              /* line number *after* the newline! */
        }
        Py_XDECREF(elem);
    }
    return root;
}


static node*
build_node_tree(PyObject *tuple)
{
    node* res = 0;
    PyObject *temp = PySequence_GetItem(tuple, 0);
    long num = -1;

    if (temp != NULL)
        num = PyInt_AsLong(temp);
    Py_XDECREF(temp);
    if (ISTERMINAL(num)) {
        /*
         *  The tuple is simple, but it doesn't start with a start symbol.
         *  Throw an exception now and be done with it.
         */
        tuple = Py_BuildValue("os", tuple,
                    "Illegal syntax-tree; cannot start with terminal symbol.");
        PyErr_SetObject(parser_error, tuple);
        Py_XDECREF(tuple);
    }
    else if (ISNONTERMINAL(num)) {
        /*
         *  Not efficient, but that can be handled later.
         */
        int line_num = 0;
        PyObject *encoding = NULL;

        if (num == encoding_decl) {
            encoding = PySequence_GetItem(tuple, 2);
            /* tuple isn't borrowed anymore here, need to DECREF */
            tuple = PySequence_GetSlice(tuple, 0, 2);
        }
        res = PyNode_New(num);
        if (res != NULL) {
            if (res != build_node_children(tuple, res, &line_num)) {
                PyNode_Free(res);
                res = NULL;
            }
            if (res && encoding) {
                Py_ssize_t len;
                len = PyString_GET_SIZE(encoding) + 1;
                res->n_str = (char *)PyObject_MALLOC(len);
                if (res->n_str != NULL)
                    (void) memcpy(res->n_str, PyString_AS_STRING(encoding), len);
                Py_DECREF(encoding);
                Py_DECREF(tuple);
            }
        }
    }
    else {
        /*  The tuple is illegal -- if the number is neither TERMINAL nor
         *  NONTERMINAL, we can't use it.  Not sure the implementation
         *  allows this condition, but the API doesn't preclude it.
         */
        PyObject *err = Py_BuildValue("os", tuple,
                                      "Illegal component tuple.");
        PyErr_SetObject(parser_error, err);
        Py_XDECREF(err);
    }

    return (res);
}


/*
 *  Validation routines used within the validation section:
 */
static int validate_terminal(node *terminal, int type, char *string);

#define validate_ampersand(ch)  validate_terminal(ch,      AMPER, "&")
#define validate_circumflex(ch) validate_terminal(ch, CIRCUMFLEX, "^")
#define validate_colon(ch)      validate_terminal(ch,      COLON, ":")
#define validate_comma(ch)      validate_terminal(ch,      COMMA, ",")
#define validate_dedent(ch)     validate_terminal(ch,     DEDENT, "")
#define validate_equal(ch)      validate_terminal(ch,      EQUAL, "=")
#define validate_indent(ch)     validate_terminal(ch,     INDENT, (char*)NULL)
#define validate_lparen(ch)     validate_terminal(ch,       LPAR, "(")
#define validate_newline(ch)    validate_terminal(ch,    NEWLINE, (char*)NULL)
#define validate_rparen(ch)     validate_terminal(ch,       RPAR, ")")
#define validate_semi(ch)       validate_terminal(ch,       SEMI, ";")
#define validate_star(ch)       validate_terminal(ch,       STAR, "*")
#define validate_vbar(ch)       validate_terminal(ch,       VBAR, "|")
#define validate_doublestar(ch) validate_terminal(ch, DOUBLESTAR, "**")
#define validate_dot(ch)        validate_terminal(ch,        DOT, ".")
#define validate_at(ch)         validate_terminal(ch,         AT, "@")
#define validate_name(ch, str)  validate_terminal(ch,       NAME, str)

#define VALIDATER(n)    static int validate_##n(node *tree)

VALIDATER(node);                VALIDATER(small_stmt);
VALIDATER(class);               VALIDATER(node);
VALIDATER(parameters);          VALIDATER(suite);
VALIDATER(testlist);            VALIDATER(varargslist);
VALIDATER(fpdef);               VALIDATER(fplist);
VALIDATER(stmt);                VALIDATER(simple_stmt);
VALIDATER(expr_stmt);           VALIDATER(power);
VALIDATER(print_stmt);          VALIDATER(del_stmt);
VALIDATER(return_stmt);         VALIDATER(list_iter);
VALIDATER(raise_stmt);          VALIDATER(import_stmt);
VALIDATER(import_name);         VALIDATER(import_from);
VALIDATER(global_stmt);         VALIDATER(list_if);
VALIDATER(assert_stmt);         VALIDATER(list_for);
VALIDATER(exec_stmt);           VALIDATER(compound_stmt);
VALIDATER(while);               VALIDATER(for);
VALIDATER(try);                 VALIDATER(except_clause);
VALIDATER(test);                VALIDATER(and_test);
VALIDATER(not_test);            VALIDATER(comparison);
VALIDATER(comp_op);             VALIDATER(expr);
VALIDATER(xor_expr);            VALIDATER(and_expr);
VALIDATER(shift_expr);          VALIDATER(arith_expr);
VALIDATER(term);                VALIDATER(factor);
VALIDATER(atom);                VALIDATER(lambdef);
VALIDATER(trailer);             VALIDATER(subscript);
VALIDATER(subscriptlist);       VALIDATER(sliceop);
VALIDATER(exprlist);            VALIDATER(dictmaker);
VALIDATER(arglist);             VALIDATER(argument);
VALIDATER(listmaker);           VALIDATER(yield_stmt);
VALIDATER(testlist1);           VALIDATER(gen_for);
VALIDATER(gen_iter);            VALIDATER(gen_if);
VALIDATER(testlist_gexp);	VALIDATER(yield_expr);
VALIDATER(yield_or_testlist);	VALIDATER(or_test);
VALIDATER(old_test); 		VALIDATER(old_lambdef);

#undef VALIDATER

#define is_even(n)      (((n) & 1) == 0)
#define is_odd(n)       (((n) & 1) == 1)


static int
validate_ntype(node *n, int t)
{
    if (TYPE(n) != t) {
        PyErr_Format(parser_error, "Expected node type %d, got %d.",
                     t, TYPE(n));
        return 0;
    }
    return 1;
}


/*  Verifies that the number of child nodes is exactly 'num', raising
 *  an exception if it isn't.  The exception message does not indicate
 *  the exact number of nodes, allowing this to be used to raise the
 *  "right" exception when the wrong number of nodes is present in a
 *  specific variant of a statement's syntax.  This is commonly used
 *  in that fashion.
 */
static int
validate_numnodes(node *n, int num, const char *const name)
{
    if (NCH(n) != num) {
        PyErr_Format(parser_error,
                     "Illegal number of children for %s node.", name);
        return 0;
    }
    return 1;
}


static int
validate_terminal(node *terminal, int type, char *string)
{
    int res = (validate_ntype(terminal, type)
               && ((string == 0) || (strcmp(string, STR(terminal)) == 0)));

    if (!res && !PyErr_Occurred()) {
        PyErr_Format(parser_error,
                     "Illegal terminal: expected \"%s\"", string);
    }
    return (res);
}


/*  X (',' X) [',']
 */
static int
validate_repeating_list(node *tree, int ntype, int (*vfunc)(node *),
                        const char *const name)
{
    int nch = NCH(tree);
    int res = (nch && validate_ntype(tree, ntype)
               && vfunc(CHILD(tree, 0)));

    if (!res && !PyErr_Occurred())
        (void) validate_numnodes(tree, 1, name);
    else {
        if (is_even(nch))
            res = validate_comma(CHILD(tree, --nch));
        if (res && nch > 1) {
            int pos = 1;
            for ( ; res && pos < nch; pos += 2)
                res = (validate_comma(CHILD(tree, pos))
                       && vfunc(CHILD(tree, pos + 1)));
        }
    }
    return (res);
}


/*  validate_class()
 *
 *  classdef:
 *      'class' NAME ['(' testlist ')'] ':' suite
 */
static int
validate_class(node *tree)
{
    int nch = NCH(tree);
    int res = (validate_ntype(tree, classdef) &&
	       	((nch == 4) || (nch == 6) || (nch == 7)));

    if (res) {
        res = (validate_name(CHILD(tree, 0), "class")
               && validate_ntype(CHILD(tree, 1), NAME)
               && validate_colon(CHILD(tree, nch - 2))
               && validate_suite(CHILD(tree, nch - 1)));
    }
    else {
        (void) validate_numnodes(tree, 4, "class");
    }
	
    if (res) {
	if (nch == 7) {
		res = ((validate_lparen(CHILD(tree, 2)) &&
			validate_testlist(CHILD(tree, 3)) &&
			validate_rparen(CHILD(tree, 4))));
	}
	else if (nch == 6) {
		res = (validate_lparen(CHILD(tree,2)) &&
			validate_rparen(CHILD(tree,3)));
	}
    }
    return (res);
}


/*  if_stmt:
 *      'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite]
 */
static int
validate_if(node *tree)
{
    int nch = NCH(tree);
    int res = (validate_ntype(tree, if_stmt)
               && (nch >= 4)
               && validate_name(CHILD(tree, 0), "if")
               && validate_test(CHILD(tree, 1))
               && validate_colon(CHILD(tree, 2))
               && validate_suite(CHILD(tree, 3)));

    if (res && ((nch % 4) == 3)) {
        /*  ... 'else' ':' suite  */
        res = (validate_name(CHILD(tree, nch - 3), "else")
               && validate_colon(CHILD(tree, nch - 2))
               && validate_suite(CHILD(tree, nch - 1)));
        nch -= 3;
    }
    else if (!res && !PyErr_Occurred())
        (void) validate_numnodes(tree, 4, "if");
    if ((nch % 4) != 0)
        /* Will catch the case for nch < 4 */
        res = validate_numnodes(tree, 0, "if");
    else if (res && (nch > 4)) {
        /*  ... ('elif' test ':' suite)+ ...  */
        int j = 4;
        while ((j < nch) && res) {
            res = (validate_name(CHILD(tree, j), "elif")
                   && validate_colon(CHILD(tree, j + 2))
                   && validate_test(CHILD(tree, j + 1))
                   && validate_suite(CHILD(tree, j + 3)));
            j += 4;
        }
    }
    return (res);
}


/*  parameters:
 *      '(' [varargslist] ')'
 *
 */
static int
validate_parameters(node *tree)
{
    int nch = NCH(tree);
    int res = validate_ntype(tree, parameters) && ((nch == 2) || (nch == 3));

    if (res) {
        res = (validate_lparen(CHILD(tree, 0))
               && validate_rparen(CHILD(tree, nch - 1)));
        if (res && (nch == 3))
            res = validate_varargslist(CHILD(tree, 1));
    }
    else {
        (void) validate_numnodes(tree, 2, "parameters");
    }
    return (res);
}


/*  validate_suite()
 *
 *  suite:
 *      simple_stmt
 *    | NEWLINE INDENT stmt+ DEDENT
 */
static int
validate_suite(node *tree)
{
    int nch = NCH(tree);
    int res = (validate_ntype(tree, suite) && ((nch == 1) || (nch >= 4)));

    if (res && (nch == 1))
        res = validate_simple_stmt(CHILD(tree, 0));
    else if (res) {
        /*  NEWLINE INDENT stmt+ DEDENT  */
        res = (validate_newline(CHILD(tree, 0))
               && validate_indent(CHILD(tree, 1))
               && validate_stmt(CHILD(tree, 2))
               && validate_dedent(CHILD(tree, nch - 1)));

        if (res && (nch > 4)) {
            int i = 3;
            --nch;                      /* forget the DEDENT     */
            for ( ; res && (i < nch); ++i)
                res = validate_stmt(CHILD(tree, i));
        }
        else if (nch < 4)
            res = validate_numnodes(tree, 4, "suite");
    }
    return (res);
}


static int
validate_testlist(node *tree)
{
    return (validate_repeating_list(tree, testlist,
                                    validate_test, "testlist"));
}


static int
validate_testlist1(node *tree)
{
    return (validate_repeating_list(tree, testlist1,
                                    validate_test, "testlist1"));
}


static int
validate_testlist_safe(node *tree)
{
    return (validate_repeating_list(tree, testlist_safe,
                                    validate_old_test, "testlist_safe"));
}


/* '*' NAME [',' '**' NAME] | '**' NAME
 */
static int
validate_varargslist_trailer(node *tree, int start)
{
    int nch = NCH(tree);
    int res = 0;
    int sym;

    if (nch <= start) {
        err_string("expected variable argument trailer for varargslist");
        return 0;
    }
    sym = TYPE(CHILD(tree, start));
    if (sym == STAR) {
        /*
         *  ('*' NAME [',' '**' NAME]
         */
        if (nch-start == 2)
            res = validate_name(CHILD(tree, start+1), NULL);
        else if (nch-start == 5)
            res = (validate_name(CHILD(tree, start+1), NULL)
                   && validate_comma(CHILD(tree, start+2))
                   && validate_doublestar(CHILD(tree, start+3))
                   && validate_name(CHILD(tree, start+4), NULL));
    }
    else if (sym == DOUBLESTAR) {
        /*
         *  '**' NAME
         */
        if (nch-start == 2)
            res = validate_name(CHILD(tree, start+1), NULL);
    }
    if (!res)
        err_string("illegal variable argument trailer for varargslist");
    return res;
}


/*  validate_varargslist()
 *
 *  varargslist:
 *      (fpdef ['=' test] ',')*
 *           ('*' NAME [',' '**' NAME]
 *         | '**' NAME)
 *    | fpdef ['=' test] (',' fpdef ['=' test])* [',']
 *
 */
static int
validate_varargslist(node *tree)
{
    int nch = NCH(tree);
    int res = validate_ntype(tree, varargslist) && (nch != 0);
    int sym;

    if (!res)
        return 0;
    if (nch < 1) {
        err_string("varargslist missing child nodes");
        return 0;
    }
    sym = TYPE(CHILD(tree, 0));
    if (sym == STAR || sym == DOUBLESTAR)
        /* whole thing matches:
         *      '*' NAME [',' '**' NAME] | '**' NAME
         */
        res = validate_varargslist_trailer(tree, 0);
    else if (sym == fpdef) {
        int i = 0;

        sym = TYPE(CHILD(tree, nch-1));
        if (sym == NAME) {
            /*
             *   (fpdef ['=' test] ',')+
             *       ('*' NAME [',' '**' NAME]
             *     | '**' NAME)
             */
            /* skip over (fpdef ['=' test] ',')+ */
            while (res && (i+2 <= nch)) {
                res = validate_fpdef(CHILD(tree, i));
                ++i;
                if (res && TYPE(CHILD(tree, i)) == EQUAL && (i+2 <= nch)) {
                    res = (validate_equal(CHILD(tree, i))
                           && validate_test(CHILD(tree, i+1)));
                    if (res)
                        i += 2;
                }
                if (res && i < nch) {
                    res = validate_comma(CHILD(tree, i));
                    ++i;
                    if (res && i < nch
                        && (TYPE(CHILD(tree, i)) == DOUBLESTAR
                            || TYPE(CHILD(tree, i)) == STAR))
                        break;
                }
            }
            /* ... '*' NAME [',' '**' NAME] | '**' NAME
             * i --^^^
             */
            if (res)
                res = validate_varargslist_trailer(tree, i);
        }
        else {
            /*
             *  fpdef ['=' test] (',' fpdef ['=' test])* [',']
             */
            /* strip trailing comma node */
            if (sym == COMMA) {
                res = validate_comma(CHILD(tree, nch-1));
                if (!res)
                    return 0;
                --nch;
            }
            /*
             *  fpdef ['=' test] (',' fpdef ['=' test])*
             */
            res = validate_fpdef(CHILD(tree, 0));
            ++i;
            if (res && (i+2 <= nch) && TYPE(CHILD(tree, i)) == EQUAL) {
                res = (validate_equal(CHILD(tree, i))
                       && validate_test(CHILD(tree, i+1)));
                i += 2;
            }
            /*
             *  ... (',' fpdef ['=' test])*
             *  i ---^^^
             */
            while (res && (nch - i) >= 2) {
                res = (validate_comma(CHILD(tree, i))
                       && validate_fpdef(CHILD(tree, i+1)));
                i += 2;
                if (res && (nch - i) >= 2 && TYPE(CHILD(tree, i)) == EQUAL) {
                    res = (validate_equal(CHILD(tree, i))
                           && validate_test(CHILD(tree, i+1)));
                    i += 2;
                }
            }
            if (res && nch - i != 0) {
                res = 0;
                err_string("illegal formation for varargslist");
            }
        }
    }
    return res;
}


/*  list_iter:  list_for | list_if
 */
static int
validate_list_iter(node *tree)
{
    int res = (validate_ntype(tree, list_iter)
               && validate_numnodes(tree, 1, "list_iter"));
    if (res && TYPE(CHILD(tree, 0)) == list_for)
        res = validate_list_for(CHILD(tree, 0));
    else
        res = validate_list_if(CHILD(tree, 0));

    return res;
}

/*  gen_iter:  gen_for | gen_if
 */
static int
validate_gen_iter(node *tree)
{
    int res = (validate_ntype(tree, gen_iter)
               && validate_numnodes(tree, 1, "gen_iter"));
    if (res && TYPE(CHILD(tree, 0)) == gen_for)
        res = validate_gen_for(CHILD(tree, 0));
    else
        res = validate_gen_if(CHILD(tree, 0));

    return res;
}

/*  list_for:  'for' exprlist 'in' testlist [list_iter]
 */
static int
validate_list_for(node *tree)
{
    int nch = NCH(tree);
    int res;

    if (nch == 5)
        res = validate_list_iter(CHILD(tree, 4));
    else
        res = validate_numnodes(tree, 4, "list_for");

    if (res)
        res = (validate_name(CHILD(tree, 0), "for")
               && validate_exprlist(CHILD(tree, 1))
               && validate_name(CHILD(tree, 2), "in")
               && validate_testlist_safe(CHILD(tree, 3)));

    return res;
}

/*  gen_for:  'for' exprlist 'in' test [gen_iter]
 */
static int
validate_gen_for(node *tree)
{
    int nch = NCH(tree);
    int res;

    if (nch == 5)
        res = validate_gen_iter(CHILD(tree, 4));
    else
        res = validate_numnodes(tree, 4, "gen_for");

    if (res)
        res = (validate_name(CHILD(tree, 0), "for")
               && validate_exprlist(CHILD(tree, 1))
               && validate_name(CHILD(tree, 2), "in")
               && validate_or_test(CHILD(tree, 3)));

    return res;
}

/*  list_if:  'if' old_test [list_iter]
 */
static int
validate_list_if(node *tree)
{
    int nch = NCH(tree);
    int res;

    if (nch == 3)
        res = validate_list_iter(CHILD(tree, 2));
    else
        res = validate_numnodes(tree, 2, "list_if");

    if (res)
        res = (validate_name(CHILD(tree, 0), "if")
               && validate_old_test(CHILD(tree, 1)));

    return res;
}

/*  gen_if:  'if' old_test [gen_iter]
 */
static int
validate_gen_if(node *tree)
{
    int nch = NCH(tree);
    int res;

    if (nch == 3)
        res = validate_gen_iter(CHILD(tree, 2));
    else
        res = validate_numnodes(tree, 2, "gen_if");
    
    if (res)
        res = (validate_name(CHILD(tree, 0), "if")
               && validate_old_test(CHILD(tree, 1)));

    return res;
}

/*  validate_fpdef()
 *
 *  fpdef:
 *      NAME
 *    | '(' fplist ')'
 */
static int
validate_fpdef(node *tree)
{
    int nch = NCH(tree);
    int res = validate_ntype(tree, fpdef);

    if (res) {
        if (nch == 1)
            res = validate_ntype(CHILD(tree, 0), NAME);
        else if (nch == 3)
            res = (validate_lparen(CHILD(tree, 0))
                   && validate_fplist(CHILD(tree, 1))
                   && validate_rparen(CHILD(tree, 2)));
        else
            res = validate_numnodes(tree, 1, "fpdef");
    }
    return (res);
}


static int
validate_fplist(node *tree)
{
    return (validate_repeating_list(tree, fplist,
                                    validate_fpdef, "fplist"));
}


/*  simple_stmt | compound_stmt
 *
 */
static int
validate_stmt(node *tree)
{
    int res = (validate_ntype(tree, stmt)
               && validate_numnodes(tree, 1, "stmt"));

    if (res) {
        tree = CHILD(tree, 0);

        if (TYPE(tree) == simple_stmt)
            res = validate_simple_stmt(tree);
        else
            res = validate_compound_stmt(tree);
    }
    return (res);
}


/*  small_stmt (';' small_stmt)* [';'] NEWLINE
 *
 */
static int
validate_simple_stmt(node *tree)
{
    int nch = NCH(tree);
    int res = (validate_ntype(tree, simple_stmt)
               && (nch >= 2)
               && validate_small_stmt(CHILD(tree, 0))
               && validate_newline(CHILD(tree, nch - 1)));

    if (nch < 2)
        res = validate_numnodes(tree, 2, "simple_stmt");
    --nch;                              /* forget the NEWLINE    */
    if (res && is_even(nch))
        res = validate_semi(CHILD(tree, --nch));
    if (res && (nch > 2)) {
        int i;

        for (i = 1; res && (i < nch); i += 2)
            res = (validate_semi(CHILD(tree, i))
                   && validate_small_stmt(CHILD(tree, i + 1)));
    }
    return (res);
}


static int
validate_small_stmt(node *tree)
{
    int nch = NCH(tree);
    int res = validate_numnodes(tree, 1, "small_stmt");

    if (res) {
        int ntype = TYPE(CHILD(tree, 0));

        if (  (ntype == expr_stmt)
              || (ntype == print_stmt)
              || (ntype == del_stmt)
              || (ntype == pass_stmt)
              || (ntype == flow_stmt)
              || (ntype == import_stmt)
              || (ntype == global_stmt)
              || (ntype == assert_stmt)
              || (ntype == exec_stmt))
            res = validate_node(CHILD(tree, 0));
        else {
            res = 0;
            err_string("illegal small_stmt child type");
        }
    }
    else if (nch == 1) {
        res = 0;
        PyErr_Format(parser_error,
                     "Unrecognized child node of small_stmt: %d.",
                     TYPE(CHILD(tree, 0)));
    }
    return (res);
}


/*  compound_stmt:
 *      if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated
 */
static int
validate_compound_stmt(node *tree)
{
    int res = (validate_ntype(tree, compound_stmt)
               && validate_numnodes(tree, 1, "compound_stmt"));
    int ntype;

    if (!res)
        return (0);

    tree = CHILD(tree, 0);
    ntype = TYPE(tree);
    if (  (ntype == if_stmt)
          || (ntype == while_stmt)
          || (ntype == for_stmt)
          || (ntype == try_stmt)
          || (ntype == with_stmt)
          || (ntype == funcdef)
          || (ntype == classdef)
          || (ntype == decorated))
        res = validate_node(tree);
    else {
        res = 0;
        PyErr_Format(parser_error,
                     "Illegal compound statement type: %d.", TYPE(tree));
    }
    return (res);
}

static int
validate_yield_or_testlist(node *tree)
{
	if (TYPE(tree) == yield_expr) 
		return validate_yield_expr(tree);
	else
		return validate_testlist(tree);
}

static int
validate_expr_stmt(node *tree)
{
    int j;
    int nch = NCH(tree);
    int res = (validate_ntype(tree, expr_stmt)
               && is_odd(nch)
               && validate_testlist(CHILD(tree, 0)));

    if (res && nch == 3
        && TYPE(CHILD(tree, 1)) == augassign) {
        res = validate_numnodes(CHILD(tree, 1), 1, "augassign")
		&& validate_yield_or_testlist(CHILD(tree, 2));

        if (res) {
            char *s = STR(CHILD(CHILD(tree, 1), 0));

            res = (strcmp(s, "+=") == 0
                   || strcmp(s, "-=") == 0
                   || strcmp(s, "*=") == 0
                   || strcmp(s, "/=") == 0
                   || strcmp(s, "//=") == 0
                   || strcmp(s, "%=") == 0
                   || strcmp(s, "&=") == 0
                   || strcmp(s, "|=") == 0…