SF patch #872326: Generator expression implementation

(Code contributed by Jiwon Seo.)

The documentation portion of the patch is being re-worked and will be
checked-in soon.  Likewise, PEP 289 will be updated to reflect Guido's
rationale for the design decisions on binding behavior (as described in
in his patch comments and in discussions on python-dev).

The test file, test_genexps.py, is written in doctest format and is
meant to exercise all aspects of the the patch.  Further additions are
welcome from everyone.  Please stress test this new feature as much as
possible before the alpha release.

20 files changed, 1503 insertions, 352 deletions

diff --git a/Doc/whatsnew/whatsnew24.tex b/Doc/whatsnew/whatsnew24.tex
index bf2c8cb..c60f28a 100644
--- a/Doc/whatsnew/whatsnew24.tex
+++ b/Doc/whatsnew/whatsnew24.tex
@@ -89,6 +89,84 @@ Greg Wilson and ultimately implemented by Raymond Hettinger.}
 XXX write this.
 
 %======================================================================
+\section{PEP 229: Generator Expressions}
+
+Generator expressions create in-line generators using a syntax similar
+to list comprehensions but with parenthesis instead of the surrounding
+brackets.
+
+Genexps allow simple generators to be constructed without a separate function
+definition.  Writing:
+       
+\begin{verbatim}
+       g = (tgtexp  for var1 in exp1  for var2 in exp2 if exp3)
+\end{verbatim}
+       
+is equivalent to:
+
+\begin{verbatim}
+    def _generator(exp):
+        for var1 in exp:
+            for var2 in exp2:
+                if exp3:
+                    yield tgtexp
+    g = _generator(exp1)
+    del _generator
+\end{verbatim}
+
+The advantage over full generator definitions is in economy of
+expression.  Their advantage over list comprehensions is in saving
+memory by creating data only when it is needed rather than forming
+a whole list is memory all at once.  Applications using memory
+friendly generator expressions may scale-up to high volumes of data
+more readily than with list comprehensions.
+
+Generator expressions are intended to be used inside functions
+such as \function{sum()}, \function{min()}, \function{set()}, and
+\function{dict()}.  These functions consume their data all at once
+and would not benefit from having a full list instead of a generator
+an input:
+
+\begin{verbatim}
+>>> sum(i*i for i in range(10))
+285
+
+>>> sorted(set(i*i for i in xrange(-10, 11)))
+[0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
+
+>>> words = "Adam apple baker Bill Nancy NASA nut".split()
+>>> dict((word.lower(), word) for word in words)
+{'apple': 'apple', 'baker': 'baker', 'bill': 'Bill', 'nasa': 'NASA',
+ 'adam': 'Adam', 'nancy': 'Nancy', 'nut': 'nut'}
+
+>>> xvec = [10, 20, 30]
+>>> yvec = [7, 5, 3]
+>>> sum(x*y for x,y in itertools.izip(xvec, yvec))     # dot product
+260
+
+\end{verbatim}     
+
+These examples show the intended use for generator expressions
+in situations where the values get consumed immediately after the
+generator is created.  In these situations, they operate like
+memory efficient versions of list comprehensions.
+
+For more complex uses of generators, it is strongly recommended that
+the traditional full generator definitions be used instead.  In a
+generator expression, the first for-loop expression is evaluated
+as soon as the expression is defined while the other expressions do
+not get evaluated until the generator is run.  This nuance is never
+an issue when the generator is used immediately.  If it is not used
+right away, then it is better to write a full generator definition
+which more clearly reveals when the expressions are evaluated and is
+more obvious about the visibility and lifetime of its looping variables.
+
+\begin{seealso}
+\seepep{289}{Generator Expressions}{Proposed by Raymond Hettinger and
+implemented by Jiwon Seo with early efforts steered by Hye-Shik Chang.}
+\end{seealso}
+
+%======================================================================
 \section{PEP 322: Reverse Iteration}
 
 A new built-in function, \function{reversed(\var{seq})}, takes a sequence
diff --git a/Grammar/Grammar b/Grammar/Grammar
index e52a544..ce75ba8 100644
--- a/Grammar/Grammar
+++ b/Grammar/Grammar
@@ -80,8 +80,9 @@ arith_expr: term (('+'|'-') term)*
 term: factor (('*'|'/'|'%'|'//') factor)*
 factor: ('+'|'-'|'~') factor | power
 power: atom trailer* ['**' factor]
-atom: '(' [testlist] ')' | '[' [listmaker] ']' | '{' [dictmaker] '}' | '`' testlist1 '`' | NAME | NUMBER | STRING+
+atom: '(' [testlist_gexp] ')' | '[' [listmaker] ']' | '{' [dictmaker] '}' | '`' testlist1 '`' | NAME | NUMBER | STRING+
 listmaker: test ( list_for | (',' test)* [','] )
+testlist_gexp: test ( gen_for | (',' test)* [','] )
 lambdef: 'lambda' [varargslist] ':' test
 trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
 subscriptlist: subscript (',' subscript)* [',']
@@ -95,12 +96,16 @@ dictmaker: test ':' test (',' test ':' test)* [',']
 classdef: 'class' NAME ['(' testlist ')'] ':' suite
 
 arglist: (argument ',')* (argument [',']| '*' test [',' '**' test] | '**' test)
-argument: [test '='] test	# Really [keyword '='] test
+argument: [test '='] test [gen_for] # Really [keyword '='] test
 
 list_iter: list_for | list_if
 list_for: 'for' exprlist 'in' testlist_safe [list_iter]
 list_if: 'if' test [list_iter]
 
+gen_iter: gen_for | gen_if
+gen_for: 'for' exprlist 'in' test [gen_iter]
+gen_if: 'if' test [gen_iter]
+
 testlist1: test (',' test)*
 
 # not used in grammar, but may appear in "node" passed from Parser to Compiler
diff --git a/Include/graminit.h b/Include/graminit.h
index 1f2ab3e..7d4a97a 100644
--- a/Include/graminit.h
+++ b/Include/graminit.h
@@ -49,20 +49,24 @@
 #define power 304
 #define atom 305
 #define listmaker 306
-#define lambdef 307
-#define trailer 308
-#define subscriptlist 309
-#define subscript 310
-#define sliceop 311
-#define exprlist 312
-#define testlist 313
-#define testlist_safe 314
-#define dictmaker 315
-#define classdef 316
-#define arglist 317
-#define argument 318
-#define list_iter 319
-#define list_for 320
-#define list_if 321
-#define testlist1 322
-#define encoding_decl 323
+#define testlist_gexp 307
+#define lambdef 308
+#define trailer 309
+#define subscriptlist 310
+#define subscript 311
+#define sliceop 312
+#define exprlist 313
+#define testlist 314
+#define testlist_safe 315
+#define dictmaker 316
+#define classdef 317
+#define arglist 318
+#define argument 319
+#define list_iter 320
+#define list_for 321
+#define list_if 322
+#define gen_iter 323
+#define gen_for 324
+#define gen_if 325
+#define testlist1 326
+#define encoding_decl 327
diff --git a/Include/symtable.h b/Include/symtable.h
index d243892..628c3e6 100644
--- a/Include/symtable.h
+++ b/Include/symtable.h
@@ -46,7 +46,7 @@ typedef struct _symtable_entry {
 				    including free refs to globals */
 	int ste_generator;       /* true if namespace is a generator */
 	int ste_opt_lineno;      /* lineno of last exec or import * */
-	int ste_tmpname;          /* temporary name counter */
+	int ste_tmpname;         /* temporary name counter */
 	struct symtable *ste_table;
 } PySymtableEntryObject;
 
@@ -93,6 +93,9 @@ PyAPI_FUNC(void) PySymtable_Free(struct symtable *);
 #define OPT_EXEC 2
 #define OPT_BARE_EXEC 4
 
+#define GENERATOR 1
+#define GENERATOR_EXPRESSION 2
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Lib/compiler/ast.py b/Lib/compiler/ast.py
index a10225b..064df50 100644
--- a/Lib/compiler/ast.py
+++ b/Lib/compiler/ast.py
@@ -1236,6 +1236,82 @@ class ListCompFor(Node):
     def __repr__(self):
         return "ListCompFor(%s, %s, %s)" % (repr(self.assign), repr(self.list), repr(self.ifs))
 
+class GenExpr(Node):
+    nodes["genexpr"] = "GenExpr"
+    def __init__(self, code):
+        self.code = code
+        self.argnames = ['[outmost-iterable]']
+        self.varargs = self.kwargs = None
+
+    def getChildren(self):
+        return self.code,
+
+    def getChildNodes(self):
+        return self.code,
+
+    def __repr__(self):
+        return "GenExpr(%s)" % (repr(self.code),)
+
+class GenExprInner(Node):
+    nodes["genexprinner"] = "GenExprInner"
+    def __init__(self, expr, quals):
+        self.expr = expr
+        self.quals = quals
+
+    def getChildren(self):
+        children = []
+        children.append(self.expr)
+        children.extend(flatten(self.quals))
+        return tuple(children)
+
+    def getChildNodes(self):
+        nodelist = []
+        nodelist.append(self.expr)
+        nodelist.extend(flatten_nodes(self.quals))
+        return tuple(nodelist)
+
+    def __repr__(self):
+        return "GenExprInner(%s, %s)" % (repr(self.expr), repr(self.quals))
+
+class GenExprFor(Node):
+    nodes["genexprfor"] = "GenExprFor"
+    def __init__(self, assign, iter, ifs):
+        self.assign = assign
+        self.iter = iter
+        self.ifs = ifs
+        self.is_outmost = False
+
+    def getChildren(self):
+        children = []
+        children.append(self.assign)
+        children.append(self.iter)
+        children.extend(flatten(self.ifs))
+        return tuple(children)
+
+    def getChildNodes(self):
+        nodelist = []
+        nodelist.append(self.assign)
+        nodelist.append(self.iter)
+        nodelist.extend(flatten_nodes(self.ifs))
+        return tuple(nodelist)
+
+    def __repr__(self):
+        return "GenExprFor(%s, %s, %s)" % (repr(self.assign), repr(self.iter), repr(self.ifs))
+
+class GenExprIf(Node):
+    nodes["genexprif"] = "GenExprIf"
+    def __init__(self, test):
+        self.test = test
+
+    def getChildren(self):
+        return self.test,
+
+    def getChildNodes(self):
+        return self.test,
+
+    def __repr__(self):
+        return "GenExprIf(%s)" % (repr(self.test),)
+
 klasses = globals()
 for k in nodes.keys():
     nodes[k] = klasses[nodes[k]]
diff --git a/Lib/compiler/pycodegen.py b/Lib/compiler/pycodegen.py
index 292e859..ef5a0d3 100644
--- a/Lib/compiler/pycodegen.py
+++ b/Lib/compiler/pycodegen.py
@@ -619,6 +619,79 @@ class CodeGenerator:
         self.newBlock()
         self.emit('POP_TOP')
 
+    def visitGenExpr(self, node):
+        gen = GenExprCodeGenerator(node, self.scopes, self.class_name,
+                                   self.get_module())
+        walk(node.code, gen)
+        gen.finish()
+        self.set_lineno(node)
+        frees = gen.scope.get_free_vars()
+        if frees:
+            for name in frees:
+                self.emit('LOAD_CLOSURE', name)
+            self.emit('LOAD_CONST', gen)
+            self.emit('MAKE_CLOSURE', 0)
+        else:
+            self.emit('LOAD_CONST', gen)
+            self.emit('MAKE_FUNCTION', 0)
+
+        # precomputation of outmost iterable
+        self.visit(node.code.quals[0].iter)
+        self.emit('GET_ITER')
+        self.emit('CALL_FUNCTION', 1)
+
+    def visitGenExprInner(self, node):
+        self.set_lineno(node)
+        # setup list
+
+        stack = []
+        for i, for_ in zip(range(len(node.quals)), node.quals):
+            start, anchor = self.visit(for_)
+            cont = None
+            for if_ in for_.ifs:
+                if cont is None:
+                    cont = self.newBlock()
+                self.visit(if_, cont)
+            stack.insert(0, (start, cont, anchor))
+
+        self.visit(node.expr)
+        self.emit('YIELD_VALUE')
+
+        for start, cont, anchor in stack:
+            if cont:
+                skip_one = self.newBlock()
+                self.emit('JUMP_FORWARD', skip_one)
+                self.startBlock(cont)
+                self.emit('POP_TOP')
+                self.nextBlock(skip_one)
+            self.emit('JUMP_ABSOLUTE', start)
+            self.startBlock(anchor)
+        self.emit('LOAD_CONST', None)
+
+    def visitGenExprFor(self, node):
+        start = self.newBlock()
+        anchor = self.newBlock()
+        
+        if node.is_outmost:
+            self.loadName('[outmost-iterable]')
+        else:
+            self.visit(node.iter)
+            self.emit('GET_ITER')
+
+        self.nextBlock(start)
+        self.set_lineno(node, force=True)
+        self.emit('FOR_ITER', anchor)
+        self.nextBlock()
+        self.visit(node.assign)
+        return start, anchor
+
+    def visitGenExprIf(self, node, branch):
+        self.set_lineno(node, force=True)
+        self.visit(node.test)
+        self.emit('JUMP_IF_FALSE', branch)
+        self.newBlock()
+        self.emit('POP_TOP')
+
     # exception related
 
     def visitAssert(self, node):
@@ -1199,6 +1272,7 @@ class AbstractFunctionCode:
             klass.lambdaCount = klass.lambdaCount + 1
         else:
             name = func.name
+
         args, hasTupleArg = generateArgList(func.argnames)
         self.graph = pyassem.PyFlowGraph(name, func.filename, args,
                                          optimized=1)
@@ -1263,6 +1337,21 @@ class FunctionCodeGenerator(NestedScopeMixin, AbstractFunctionCode,
         if self.scope.generator is not None:
             self.graph.setFlag(CO_GENERATOR)
 
+class GenExprCodeGenerator(NestedScopeMixin, AbstractFunctionCode,
+                           CodeGenerator):
+    super_init = CodeGenerator.__init__ # call be other init
+    scopes = None
+
+    __super_init = AbstractFunctionCode.__init__
+
+    def __init__(self, gexp, scopes, class_name, mod):
+        self.scopes = scopes
+        self.scope = scopes[gexp]
+        self.__super_init(gexp, scopes, 1, class_name, mod)
+        self.graph.setFreeVars(self.scope.get_free_vars())
+        self.graph.setCellVars(self.scope.get_cell_vars())
+        self.graph.setFlag(CO_GENERATOR)
+
 class AbstractClassCode:
 
     def __init__(self, klass, scopes, module):
diff --git a/Lib/compiler/symbols.py b/Lib/compiler/symbols.py
index fa668f1..6843e19 100644
--- a/Lib/compiler/symbols.py
+++ b/Lib/compiler/symbols.py
@@ -179,6 +179,21 @@ class ModuleScope(Scope):
 class FunctionScope(Scope):
     pass
 
+class GenExprScope(Scope):
+    __super_init = Scope.__init__
+
+    __counter = 1
+
+    def __init__(self, module, klass=None):
+        i = self.__counter
+        self.__counter += 1
+        self.__super_init("generator expression<%d>"%i, module, klass)
+        self.add_param('[outmost-iterable]')
+
+    def get_names(self):
+        keys = Scope.get_names()
+        return keys
+
 class LambdaScope(FunctionScope):
     __super_init = Scope.__init__
 
@@ -220,6 +235,32 @@ class SymbolVisitor:
         self.visit(node.code, scope)
         self.handle_free_vars(scope, parent)
 
+    def visitGenExpr(self, node, parent):
+        scope = GenExprScope(self.module, self.klass);
+        if parent.nested or isinstance(parent, FunctionScope) \
+                or isinstance(parent, GenExprScope):
+            scope.nested = 1
+
+        self.scopes[node] = scope
+        self.visit(node.code, scope)
+
+        self.handle_free_vars(scope, parent)
+
+    def visitGenExprInner(self, node, scope):
+        for genfor in node.quals:
+            self.visit(genfor, scope)
+
+        self.visit(node.expr, scope)
+
+    def visitGenExprFor(self, node, scope):
+        self.visit(node.assign, scope, 1)
+        self.visit(node.iter, scope)
+        for if_ in node.ifs:
+            self.visit(if_, scope)
+
+    def visitGenExprIf(self, node, scope):
+        self.visit(node.test, scope)
+        
     def visitLambda(self, node, parent, assign=0):
         # Lambda is an expression, so it could appear in an expression
         # context where assign is passed.  The transformer should catch
diff --git a/Lib/compiler/transformer.py b/Lib/compiler/transformer.py
index 9074fc7..6832cf1 100644
--- a/Lib/compiler/transformer.py
+++ b/Lib/compiler/transformer.py
@@ -534,6 +534,12 @@ class Transformer:
     testlist1 = testlist
     exprlist = testlist
 
+    def testlist_gexp(self, nodelist):
+        if len(nodelist) == 2 and nodelist[1][0] == symbol.gen_for:
+            test = self.com_node(nodelist[0])
+            return self.com_generator_expression(test, nodelist[1])
+        return self.testlist(nodelist)
+
     def test(self, nodelist):
         # and_test ('or' and_test)* | lambdef
         if len(nodelist) == 1 and nodelist[0][0] == symbol.lambdef:
@@ -1085,6 +1091,48 @@ class Transformer:
                 values.append(self.com_node(nodelist[i]))
             return List(values)
 
+    if hasattr(symbol, 'gen_for'):
+        def com_generator_expression(self, expr, node):
+            # gen_iter: gen_for | gen_if
+            # gen_for: 'for' exprlist 'in' test [gen_iter]
+            # gen_if: 'if' test [gen_iter]
+
+            lineno = node[1][2]
+            fors = []
+            while node:
+                t = node[1][1]
+                if t == 'for':
+                    assignNode = self.com_assign(node[2], OP_ASSIGN)
+                    genNode = self.com_node(node[4])
+                    newfor = GenExprFor(assignNode, genNode, [])
+                    newfor.lineno = node[1][2]
+                    fors.append(newfor)
+                    if (len(node)) == 5:
+                        node = None
+                    else:
+                        node = self.com_gen_iter(node[5])
+                elif t == 'if':
+                    test = self.com_node(node[2])
+                    newif = GenExprIf(test)
+                    newif.lineno = node[1][2]
+                    newfor.ifs.append(newif)
+                    if len(node) == 3:
+                        node = None
+                    else:
+                        node = self.com_gen_iter(node[3])
+                else:
+                    raise SyntaxError, \
+                            ("unexpected generator expression element: %s %d"
+                             % (node, lineno))
+            fors[0].is_outmost = True
+            n = GenExpr(GenExprInner(expr, fors))
+            n.lineno = lineno
+            return n
+
+        def com_gen_iter(self, node):
+            assert node[0] == symbol.gen_iter
+            return node[1]
+
     def com_dictmaker(self, nodelist):
         # dictmaker: test ':' test (',' test ':' value)* [',']
         items = []
@@ -1122,6 +1170,8 @@ class Transformer:
             if node[0] == token.STAR or node[0] == token.DOUBLESTAR:
                 break
             kw, result = self.com_argument(node, kw)
+            if len_nodelist != 2 and isinstance(result, GenExpr):
+                raise SyntaxError, 'generator expression needs parenthesis'
             args.append(result)
         else:
             # No broken by star arg, so skip the last one we processed.
@@ -1148,6 +1198,9 @@ class Transformer:
         return CallFunc(primaryNode, args, star_node, dstar_node)
 
     def com_argument(self, nodelist, kw):
+        if len(nodelist) == 3 and nodelist[2][0] == symbol.gen_for:
+            test = self.com_node(nodelist[1])
+            return 0, self.com_generator_expression(test, nodelist[2])
         if len(nodelist) == 2:
             if kw:
                 raise SyntaxError, "non-keyword arg after keyword arg"
diff --git a/Lib/symbol.py b/Lib/symbol.py
index 38c6193..c839e4a 100755
--- a/Lib/symbol.py
+++ b/Lib/symbol.py
@@ -61,23 +61,27 @@ factor = 303
 power = 304
 atom = 305
 listmaker = 306
-lambdef = 307
-trailer = 308
-subscriptlist = 309
-subscript = 310
-sliceop = 311
-exprlist = 312
-testlist = 313
-testlist_safe = 314
-dictmaker = 315
-classdef = 316
-arglist = 317
-argument = 318
-list_iter = 319
-list_for = 320
-list_if = 321
-testlist1 = 322
-encoding_decl = 323
+testlist_gexp = 307
+lambdef = 308
+trailer = 309
+subscriptlist = 310
+subscript = 311
+sliceop = 312
+exprlist = 313
+testlist = 314
+testlist_safe = 315
+dictmaker = 316
+classdef = 317
+arglist = 318
+argument = 319
+list_iter = 320
+list_for = 321
+list_if = 322
+gen_iter = 323
+gen_for = 324
+gen_if = 325
+testlist1 = 326
+encoding_decl = 327
 #--end constants--
 
 sym_name = {}
diff --git a/Lib/test/test_deque.py b/Lib/test/test_deque.py
index 9b857c5..bad8857 100644
--- a/Lib/test/test_deque.py
+++ b/Lib/test/test_deque.py
@@ -566,7 +566,7 @@ def test_main(verbose=None):
 
     # doctests
     from test import test_deque
-#    test_support.run_doctest(test_deque, verbose)
+    test_support.run_doctest(test_deque, verbose)
 
 if __name__ == "__main__":
     test_main(verbose=True)
diff --git a/Lib/test/test_genexps.py b/Lib/test/test_genexps.py
new file mode 100644
index 0000000..b09fc95
--- /dev/null
+++ b/Lib/test/test_genexps.py
@@ -0,0 +1,258 @@
+doctests = """
+
+Test simple loop with conditional
+
+    >>> sum(i*i for i in range(100) if i&1 == 1)
+    166650
+
+Test simple nesting
+
+    >>> list((i,j) for i in range(3) for j in range(4) )
+    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
+
+Test nesting with the inner expression dependent on the outer
+
+    >>> list((i,j) for i in range(4) for j in range(i) )
+    [(1, 0), (2, 0), (2, 1), (3, 0), (3, 1), (3, 2)]
+
+Make sure the induction variable is not exposed
+
+    >>> i = 20
+    >>> sum(i*i for i in range(100))
+    328350
+    >>> i
+    20
+
+Test first class
+
+    >>> g = (i*i for i in range(4))
+    >>> type(g)
+    <type 'generator'>
+    >>> list(g)
+    [0, 1, 4, 9]
+
+Test direct calls to next()
+
+    >>> g = (i*i for i in range(3))
+    >>> g.next()
+    0
+    >>> g.next()
+    1
+    >>> g.next()
+    4
+    >>> g.next()
+    Traceback (most recent call last):
+      File "<pyshell#21>", line 1, in -toplevel-
+        g.next()
+    StopIteration
+
+Does it stay stopped?
+
+    >>> g.next()
+    Traceback (most recent call last):
+      File "<pyshell#21>", line 1, in -toplevel-
+        g.next()
+    StopIteration
+    >>> list(g)
+    []
+
+Test running gen when defining function is out of scope
+
+    >>> def f(n):
+    ...     return (i*i for i in xrange(n))
+    ...
+    >>> list(f(10))
+    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
+
+    >>> def f(n):
+    ...     return ((i,j) for i in xrange(3) for j in xrange(n))
+    ...
+    >>> list(f(4))
+    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
+    >>> def f(n):
+    ...     return ((i,j) for i in xrange(3) for j in xrange(4) if j in xrange(n))
+    ...
+    >>> list(f(4))
+    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
+    >>> list(f(2))
+    [(0, 0), (0, 1), (1, 0), (1, 1), (2, 0), (2, 1)]
+
+#Verify that parenthesis are required in a statement
+#>>> def f(n):
+#...     return i*i for i in xrange(n)
+#...
+#SyntaxError: invalid syntax
+
+Verify early binding for the outermost for-expression
+
+    >>> x=10
+    >>> g = (i*i for i in range(x))
+    >>> x = 5
+    >>> list(g)
+    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
+
+Verify late binding for the outermost if-expression
+
+    >>> include = (2,4,6,8)
+    >>> g = (i*i for i in range(10) if i in include)
+    >>> include = (1,3,5,7,9)
+    >>> list(g)
+    [1, 9, 25, 49, 81]
+
+Verify late binding for the innermost for-expression
+
+    >>> g = ((i,j) for i in range(3) for j in range(x))
+    >>> x = 4
+    >>> list(g)
+    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
+
+Verify re-use of tuples (a side benefit of using genexps over listcomps)
+
+    >>> tupleids = map(id, ((i,i) for i in xrange(10)))
+    >>> max(tupleids) - min(tupleids)
+    0
+
+
+
+########### Tests borrowed from or inspired by test_generators.py ############
+
+Make a generator that acts like range()
+
+    >>> yrange = lambda n:  (i for i in xrange(n))
+    >>> list(yrange(10))
+    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+Generators always return to the most recent caller:
+
+    >>> def creator():
+    ...     r = yrange(5)
+    ...     print "creator", r.next()
+    ...     return r
+    ...
+    >>> def caller():
+    ...     r = creator()
+    ...     for i in r:
+    ...             print "caller", i
+    ...
+    >>> caller()
+    creator 0
+    caller 1
+    caller 2
+    caller 3
+    caller 4
+
+Generators can call other generators:
+
+    >>> def zrange(n):
+    ...     for i in yrange(n):
+    ...         yield i
+    ...
+    >>> list(zrange(5))
+    [0, 1, 2, 3, 4]
+
+
+Verify that a gen exp cannot be resumed while it is actively running:
+
+    >>> g = (me.next() for i in xrange(10))
+    >>> me = g
+    >>> me.next()
+    Traceback (most recent call last):
+      File "<pyshell#30>", line 1, in -toplevel-
+        me.next()
+      File "<pyshell#28>", line 1, in <generator expression>
+        g = (me.next() for i in xrange(10))
+    ValueError: generator already executing
+
+Verify exception propagation
+
+    >>> g = (10 // i for i in (5, 0, 2))
+    >>> g.next()
+    2
+    >>> g.next()
+    Traceback (most recent call last):
+      File "<pyshell#37>", line 1, in -toplevel-
+        g.next()
+      File "<pyshell#35>", line 1, in <generator expression>
+        g = (10 // i for i in (5, 0, 2))
+    ZeroDivisionError: integer division or modulo by zero
+    >>> g.next()
+    Traceback (most recent call last):
+      File "<pyshell#38>", line 1, in -toplevel-
+        g.next()
+    StopIteration
+
+Make sure that None is a valid return value
+
+    >>> list(None for i in xrange(10))
+    [None, None, None, None, None, None, None, None, None, None]
+
+Check that generator attributes are present
+
+    >>> g = (i*i for i in range(3))
+    >>> expected = set(['gi_frame', 'gi_running', 'next'])
+    >>> set(attr for attr in dir(g) if not attr.startswith('__')) >= expected
+    True
+
+    >>> print g.next.__doc__
+    x.next() -> the next value, or raise StopIteration
+    >>> import types
+    >>> isinstance(g, types.GeneratorType)
+    True
+
+Check the __iter__ slot is defined to return self
+
+    >>> iter(g) is g
+    True
+
+Verify that the running flag is set properly
+
+    >>> g = (me.gi_running for i in (0,1))
+    >>> me = g
+    >>> me.gi_running
+    0
+    >>> me.next()
+    1
+    >>> me.gi_running
+    0
+
+Verify that genexps are weakly referencable
+
+    >>> import weakref
+    >>> g = (i*i for i in range(4))
+    >>> wr = weakref.ref(g)
+    >>> wr() is g
+    True
+    >>> p = weakref.proxy(g)
+    >>> list(p)
+    [0, 1, 4, 9]
+
+
+"""
+
+
+__test__ = {'doctests' : doctests}
+
+def test_main(verbose=None):
+    import sys
+    from test import test_support
+    from test import test_genexps
+    test_support.run_doctest(test_genexps, verbose)
+
+    # verify reference counting
+    if verbose and hasattr(sys, "gettotalrefcount"):
+        import gc
+        counts = [None] * 5
+        for i in xrange(len(counts)):
+            test_support.run_doctest(test_genexps, verbose)
+            gc.collect()
+            counts[i] = sys.gettotalrefcount()
+        print counts
+
+if __name__ == "__main__":
+    test_main(verbose=True)
+
+
+
+
+
+
diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index 0eed4bb..e0d5b74 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -739,3 +739,46 @@ print [
         for (sp_sno, sp_pno) in suppart
           if sno == sp_sno and pno == sp_pno
 ]
+
+# generator expression tests
+g = ([x for x in range(10)] for x in range(1))
+verify(g.next() == [x for x in range(10)])
+try:
+    g.next()
+    raise TestFailed, 'should produce StopIteration exception'
+except StopIteration:
+    pass
+
+a = 1
+try:
+    g = (a for d in a)
+    g.next()
+    raise TestFailed, 'should produce TypeError'
+except TypeError:
+    pass
+
+verify(list((x, y) for x in 'abcd' for y in 'abcd') == [(x, y) for x in 'abcd' for y in 'abcd'])
+verify(list((x, y) for x in 'ab' for y in 'xy') == [(x, y) for x in 'ab' for y in 'xy'])
+
+a = [x for x in range(10)]
+b = (x for x in (y for y in a))
+verify(sum(b) == sum([x for x in range(10)]))
+
+verify(sum(x**2 for x in range(10)) == sum([x**2 for x in range(10)]))
+verify(sum(x*x for x in range(10) if x%2) == sum([x*x for x in range(10) if x%2]))
+verify(sum(x for x in (y for y in range(10))) == sum([x for x in range(10)]))
+verify(sum(x for x in (y for y in (z for z in range(10)))) == sum([x for x in range(10)]))
+verify(sum(x for x in [y for y in (z for z in range(10))]) == sum([x for x in range(10)]))
+verify(sum(x for x in (y for y in (z for z in range(10) if True)) if True) == sum([x for x in range(10)]))
+verify(sum(x for x in (y for y in (z for z in range(10) if True) if False) if True) == 0)
+check_syntax("foo(x for x in range(10), 100)")
+check_syntax("foo(100, x for x in range(10))")
+
+# test for outmost iterable precomputation
+x = 10; g = (i for i in range(x)); x = 5
+verify(len(list(g)) == 10)
+
+# This should hold, since we're only precomputing outmost iterable.
+x = 10; t = False; g = ((i,j) for i in range(x) if t for j in range(x))
+x = 5; t = True;
+verify([(i,j) for i in range(10) for j in range(5)] == list(g))
diff --git a/Lib/test/test_parser.py b/Lib/test/test_parser.py
index 7860e7b..9652f6b 100644
--- a/Lib/test/test_parser.py
+++ b/Lib/test/test_parser.py
@@ -67,6 +67,8 @@ class RoundtripLegalSyntaxTestCase(unittest.TestCase):
         self.check_expr("lambda foo=bar, blaz=blat+2, **z: 0")
         self.check_expr("lambda foo=bar, blaz=blat+2, *y, **z: 0")
         self.check_expr("lambda x, *y, **z: 0")
+        self.check_expr("(x for x in range(10))")
+        self.check_expr("foo(x for x in range(10))")
 
     def test_print(self):
         self.check_suite("print")
diff --git a/Misc/ACKS b/Misc/ACKS
index f91b65d..fb3c94f 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -500,6 +500,7 @@ Barry Scott
 Steven Scott
 Nick Seidenman
 Fred Sells
+Jiwon Seo
 Denis Severson
 Ha Shao
 Bruce Sherwood
diff --git a/Misc/NEWS b/Misc/NEWS
index f111d0e..58ad98c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@ What's New in Python 2.4 alpha 1?
 Core and builtins
 -----------------
 
+- Implemented generator expressions (PEP 289).  Coded by Jiwon Seo.
+
 - Enabled the profiling of C extension functions (and builtins) - check
   new documentation and modified profiler and bdb modules for more details
 
diff --git a/Modules/parsermodule.c b/Modules/parsermodule.c
index bf6a360..35c5dee 100644
--- a/Modules/parsermodule.c
+++ b/Modules/parsermodule.c
@@ -855,7 +855,9 @@ VALIDATER(subscriptlist);       VALIDATER(sliceop);
 VALIDATER(exprlist);            VALIDATER(dictmaker);
 VALIDATER(arglist);             VALIDATER(argument);
 VALIDATER(listmaker);           VALIDATER(yield_stmt);
-VALIDATER(testlist1);
+VALIDATER(testlist1);           VALIDATER(gen_for);
+VALIDATER(gen_iter);            VALIDATER(gen_if);
+VALIDATER(testlist_gexp);
 
 #undef VALIDATER
 
@@ -1246,6 +1248,21 @@ validate_list_iter(node *tree)
     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
@@ -1268,6 +1285,28 @@ validate_list_for(node *tree)
     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_test(CHILD(tree, 3)));
+
+    return res;
+}
+
 /*  list_if:  'if' test [list_iter]
  */
 static int
@@ -1288,6 +1327,25 @@ validate_list_if(node *tree)
     return res;
 }
 
+/*  gen_if:  'if' 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_test(CHILD(tree, 1)));
+
+    return res;
+}
 
 /*  validate_fpdef()
  *
@@ -2187,7 +2245,7 @@ validate_atom(node *tree)
                    && (validate_rparen(CHILD(tree, nch - 1))));
 
             if (res && (nch == 3))
-                res = validate_testlist(CHILD(tree, 1));
+                res = validate_testlist_gexp(CHILD(tree, 1));
             break;
           case LSQB:
             if (nch == 2)
@@ -2244,7 +2302,7 @@ validate_listmaker(node *tree)
         ok = validate_test(CHILD(tree, 0));
 
     /*
-     *  list_iter | (',' test)* [',']
+     *  list_for | (',' test)* [',']
      */
     if (nch == 2 && TYPE(CHILD(tree, 1)) == list_for)
         ok = validate_list_for(CHILD(tree, 1));
@@ -2266,6 +2324,43 @@ validate_listmaker(node *tree)
     return ok;
 }
 
+/*  testlist_gexp:
+ *    test ( gen_for | (',' test)* [','] )
+ */
+static int
+validate_testlist_gexp(node *tree)
+{
+    int nch = NCH(tree);
+    int ok = nch;
+
+    if (nch == 0)
+        err_string("missing child nodes of testlist_gexp");
+    else {
+        ok = validate_test(CHILD(tree, 0));
+    }
+
+    /*
+     *  gen_for | (',' test)* [',']
+     */
+    if (nch == 2 && TYPE(CHILD(tree, 1)) == gen_for)
+        ok = validate_gen_for(CHILD(tree, 1));
+    else {
+        /*  (',' test)* [',']  */
+        int i = 1;
+        while (ok && nch - i >= 2) {
+            ok = (validate_comma(CHILD(tree, i))
+                  && validate_test(CHILD(tree, i+1)));
+            i += 2;
+        }
+        if (ok && i == nch-1)
+            ok = validate_comma(CHILD(tree, i));
+        else if (i != nch) {
+            ok = 0;
+            err_string("illegal trailing nodes for testlist_gexp");
+        }
+    }
+    return ok;
+}
 
 /*  funcdef:
  *      'def' NAME parameters ':' suite
@@ -2318,6 +2413,18 @@ validate_arglist(node *tree)
         /* raise the right error from having an invalid number of children */
         return validate_numnodes(tree, nch + 1, "arglist");
 
+    if (nch > 1) {
+        for (i=0; i<nch; i++) {
+            if (TYPE(CHILD(tree, i)) == argument) {
+                node *ch = CHILD(tree, i);
+                if (NCH(ch) == 2 && TYPE(CHILD(ch, 1)) == gen_for) {
+                    err_string("need '(', ')' for generator expression");
+                    return 0;
+                }
+            }
+        }
+    }
+
     while (ok && nch-i >= 2) {
         /* skip leading (argument ',') */
         ok = (validate_argument(CHILD(tree, i))
@@ -2377,17 +2484,19 @@ validate_arglist(node *tree)
 
 /*  argument:
  *
- *  [test '='] test
+ *  [test '='] test [gen_for]
  */
 static int
 validate_argument(node *tree)
 {
     int nch = NCH(tree);
     int res = (validate_ntype(tree, argument)
-               && ((nch == 1) || (nch == 3))
+               && ((nch == 1) || (nch == 2) || (nch == 3))
                && validate_test(CHILD(tree, 0)));
 
-    if (res && (nch == 3))
+    if (res && (nch == 2))
+        res = validate_gen_for(CHILD(tree, 1));
+    else if (res && (nch == 3))
         res = (validate_equal(CHILD(tree, 1))
                && validate_test(CHILD(tree, 2)));
 
diff --git a/Python/compile.c b/Python/compile.c
index 7bbcd62..15159f8 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -744,11 +744,15 @@ static int com_add(struct compiling *, PyObject *, PyObject *, PyObject *);
 static int com_addconst(struct compiling *, PyObject *);
 static int com_addname(struct compiling *, PyObject *);
 static void com_addopname(struct compiling *, int, node *);
+static void com_test(struct compiling *c, node *n);
 static void com_list(struct compiling *, node *, int);
 static void com_list_iter(struct compiling *, node *, node *, char *);
+static void com_gen_iter(struct compiling *, node *, node *);
 static int com_argdefs(struct compiling *, node *);
 static void com_assign(struct compiling *, node *, int, node *);
 static void com_assign_name(struct compiling *, node *, int);
+static int com_make_closure(struct compiling *c, PyCodeObject *co);
+
 static PyCodeObject *icompile(node *, struct compiling *);
 static PyCodeObject *jcompile(node *, const char *, struct compiling *,
 			      PyCompilerFlags *);
@@ -759,6 +763,7 @@ static node *get_rawdocstring(node *);
 static int get_ref_type(struct compiling *, char *);
 
 /* symtable operations */
+static int symtable_lookup(struct symtable *st, char *name);
 static struct symtable *symtable_build(node *, PyFutureFeatures *,
 				       const char *filename);
 static int symtable_load_symbols(struct compiling *);
@@ -777,7 +782,10 @@ static void symtable_global(struct symtable *, node *);
 static void symtable_import(struct symtable *, node *);
 static void symtable_assign(struct symtable *, node *, int);
 static void symtable_list_comprehension(struct symtable *, node *);
+static void symtable_generator_expression(struct symtable *, node *);
 static void symtable_list_for(struct symtable *, node *);
+static void symtable_gen_for(struct symtable *, node *, int);
+static void symtable_gen_iter(struct symtable *, node *);
 
 static int symtable_update_free_vars(struct symtable *);
 static int symtable_undo_free(struct symtable *, PyObject *, PyObject *);
@@ -1589,7 +1597,7 @@ com_list_for(struct compiling *c, node *n, node *e, char *t)
 	int anchor = 0;
 	int save_begin = c->c_begin;
 
-	/* list_iter: for v in expr [list_iter] */
+	/* list_for: for v in expr [list_iter] */
 	com_node(c, CHILD(n, 3)); /* expr */
 	com_addbyte(c, GET_ITER);
 	c->c_begin = c->c_nexti;
@@ -1606,6 +1614,52 @@ com_list_for(struct compiling *c, node *n, node *e, char *t)
 }  
 
 static void
+com_gen_for(struct compiling *c, node *n, node *t, int is_outmost)
+{
+	int break_anchor = 0;
+	int anchor = 0;
+	int save_begin = c->c_begin;
+
+	REQ(n, gen_for);
+	/* gen_for: for v in test [gen_iter] */
+
+	com_addfwref(c, SETUP_LOOP, &break_anchor);
+	block_push(c, SETUP_LOOP);
+
+	if (is_outmost) {
+		com_addop_varname(c, VAR_LOAD, "[outmost-iterable]");
+		com_push(c, 1);
+	}
+	else {
+		com_node(c, CHILD(n, 3));
+		com_addbyte(c, GET_ITER); 
+	}
+
+	c->c_begin = c->c_nexti;
+	com_set_lineno(c, c->c_last_line);
+	com_addfwref(c, FOR_ITER, &anchor);
+	com_push(c, 1);
+	com_assign(c, CHILD(n, 1), OP_ASSIGN, NULL);
+
+	if (NCH(n) == 5) 
+		com_gen_iter(c, CHILD(n, 4), t);
+	else {
+		com_test(c, t);
+		com_addbyte(c, YIELD_VALUE);
+		com_pop(c, 1);
+	}
+
+	com_addoparg(c, JUMP_ABSOLUTE, c->c_begin);
+	c->c_begin = save_begin;
+
+	com_backpatch(c, anchor);
+	com_pop(c, 1); /* FOR_ITER has popped this */
+	com_addbyte(c, POP_BLOCK);
+	block_pop(c, SETUP_LOOP);
+	com_backpatch(c, break_anchor);
+}
+
+static void
 com_list_if(struct compiling *c, node *n, node *e, char *t)
 {
 	int anchor = 0;
@@ -1624,6 +1678,32 @@ com_list_if(struct compiling *c, node *n, node *e, char *t)
 }
 
 static void
+com_gen_if(struct compiling *c, node *n, node *t)
+{
+	/* gen_if: 'if' test [gen_iter] */
+	int anchor = 0;
+	int a=0;
+
+	com_node(c, CHILD(n, 1));
+	com_addfwref(c, JUMP_IF_FALSE, &a);
+	com_addbyte(c, POP_TOP);
+	com_pop(c, 1);
+
+	if (NCH(n) == 3)
+		com_gen_iter(c, CHILD(n, 2), t);
+	else {
+		com_test(c, t);
+		com_addbyte(c, YIELD_VALUE);
+		com_pop(c, 1);
+	}
+	com_addfwref(c, JUMP_FORWARD, &anchor);
+	com_backpatch(c, a);
+	/* We jump here with an extra entry which we now pop */
+	com_addbyte(c, POP_TOP);
+	com_backpatch(c, anchor);
+}
+
+static void
 com_list_iter(struct compiling *c,
 	      node *p,		/* parent of list_iter node */
 	      node *e,		/* element expression node */
@@ -1655,6 +1735,28 @@ com_list_iter(struct compiling *c,
 }
 
 static void
+com_gen_iter(struct compiling *c, node *n, node *t)
+{
+	/* gen_iter: gen_for | gen_if */
+	node *ch;
+	REQ(n, gen_iter);
+
+	ch = CHILD(n, 0);
+
+	switch (TYPE(ch)) {
+	case gen_for:
+		com_gen_for(c, ch, t, 0);
+		break;
+	case gen_if:
+		com_gen_if(c, ch, t);
+		break;
+	default:
+		com_error(c, PyExc_SystemError,
+			  "invalid gen_iter node type");
+	}
+}
+
+static void
 com_list_comprehension(struct compiling *c, node *n)
 {
 	/* listmaker: test list_for */
@@ -1689,6 +1791,52 @@ com_listmaker(struct compiling *c, node *n)
 }
 
 static void
+com_generator_expression(struct compiling *c, node *n)
+{
+	/* testlist_gexp: test gen_for */
+	/* argument: test gen_for */
+	PyCodeObject *co;
+
+	REQ(CHILD(n, 0), test); 
+	REQ(CHILD(n, 1), gen_for); 
+
+	symtable_enter_scope(c->c_symtable, "<genexpr>", TYPE(n),
+		             n->n_lineno);
+	co = icompile(n, c);
+	symtable_exit_scope(c->c_symtable);
+
+	if (co == NULL)
+		c->c_errors++;
+	else {
+		int closure = com_make_closure(c, co);
+		int i = com_addconst(c, (PyObject *)co);
+
+		com_addoparg(c, LOAD_CONST, i);
+		com_push(c, 1);
+		if (closure)
+			com_addoparg(c, MAKE_CLOSURE, 0);
+		else
+			com_addoparg(c, MAKE_FUNCTION, 0);
+
+		com_test(c, CHILD(CHILD(n, 1), 3));
+		com_addbyte(c, GET_ITER);
+		com_addoparg(c, CALL_FUNCTION, 1);
+		com_pop(c, 1);
+
+		Py_DECREF(co);
+	}
+}
+
+static void
+com_testlist_gexp(struct compiling *c, node *n)
+{
+	/* testlist_gexp: test ( gen_for | (',' test)* [','] ) */
+	if (NCH(n) > 1 && TYPE(CHILD(n, 1)) == gen_for)
+		com_generator_expression(c, n);
+	else com_list(c, n, 0);
+}
+
+static void
 com_dictmaker(struct compiling *c, node *n)
 {
 	int i;
@@ -1721,7 +1869,7 @@ com_atom(struct compiling *c, node *n)
 			com_push(c, 1);
 		}
 		else
-			com_node(c, CHILD(n, 1));
+			com_testlist_gexp(c, CHILD(n, 1));
 		break;
 	case LSQB: /* '[' [listmaker] ']' */
 		if (TYPE(CHILD(n, 1)) == RSQB) {
@@ -1857,7 +2005,7 @@ static void
 com_argument(struct compiling *c, node *n, PyObject **pkeywords)
 {
 	node *m;
-	REQ(n, argument); /* [test '='] test; really [keyword '='] test */
+	REQ(n, argument); /* [test '='] test [gen_for]; really [keyword '='] test */
 	if (NCH(n) == 1) {
 		if (*pkeywords != NULL) {
 			com_error(c, PyExc_SyntaxError,
@@ -1868,6 +2016,11 @@ com_argument(struct compiling *c, node *n, PyObject **pkeywords)
 		}
 		return;
 	}
+	if (NCH(n) == 2) {
+		com_generator_expression(c, n);
+		return;
+	}
+
 	m = n;
 	do {
 		m = CHILD(m, 0);
@@ -2723,7 +2876,8 @@ static void
 com_assign_sequence(struct compiling *c, node *n, int assigning)
 {
 	int i;
-	if (TYPE(n) != testlist && TYPE(n) != listmaker)
+	if (TYPE(n) != testlist && TYPE(n) != testlist_gexp &&
+	    TYPE(n) != listmaker)
 		REQ(n, exprlist);
 	if (assigning) {
 		i = (NCH(n)+1)/2;
@@ -2765,7 +2919,13 @@ com_assign(struct compiling *c, node *n, int assigning, node *augn)
 		case exprlist:
 		case testlist:
 		case testlist1:
+		case testlist_gexp:
 			if (NCH(n) > 1) {
+				if (TYPE(CHILD(n, 1)) == gen_for) {
+					com_error(c, PyExc_SystemError,
+				  "assign to generator expression not possible");
+					return;
+				}
 				if (assigning > OP_APPLY) {
 					com_error(c, PyExc_SyntaxError,
 				  "augmented assign to tuple not possible");
@@ -4253,6 +4413,23 @@ compile_classdef(struct compiling *c, node *n)
 }
 
 static void
+compile_generator_expression(struct compiling *c, node *n)
+{
+	/* testlist_gexp: test gen_for */
+	/* argument: test gen_for */
+	REQ(CHILD(n, 0), test); 
+	REQ(CHILD(n, 1), gen_for); 
+
+	c->c_name = "<generator expression>";
+	com_gen_for(c, CHILD(n, 1), CHILD(n, 0), 1);
+
+	com_addoparg(c, LOAD_CONST, com_addconst(c, Py_None));
+	com_push(c, 1);
+	com_addbyte(c, RETURN_VALUE);
+	com_pop(c, 1);
+}
+
+static void
 compile_node(struct compiling *c, node *n)
 {
 	com_set_lineno(c, n->n_lineno);
@@ -4300,6 +4477,11 @@ compile_node(struct compiling *c, node *n)
 		compile_classdef(c, n);
 		break;
 	
+	case testlist_gexp: /* A generator expression */
+	case argument:      /* A generator expression */
+		compile_generator_expression(c, n);
+		break;
+
 	default:
 		com_error(c, PyExc_SystemError,
 			  "compile_node: unexpected node type");
@@ -4976,7 +5158,6 @@ symtable_load_symbols(struct compiling *c)
 			}
 		}
 	}
-
 	assert(PyDict_Size(c->c_freevars) == si.si_nfrees);
 
 	if (si.si_ncells > 1) { /* one cell is always in order */
@@ -5346,11 +5527,11 @@ look_for_yield(node *n)
 			return 0;
 
 		case yield_stmt:
-			return 1;
+			return GENERATOR;
 
 		default:
 			if (look_for_yield(kid))
-				return 1;
+				return GENERATOR;
 		}
 	}
 	return 0;
@@ -5494,6 +5675,18 @@ symtable_node(struct symtable *st, node *n)
 			if (TYPE(CHILD(n, i)) >= single_input)
 				symtable_node(st, CHILD(n, i));
 		break;
+	case arglist:
+		if (NCH(n) > 1)
+			for (i = 0; i < NCH(n); ++i) {
+				node *ch = CHILD(n, i);
+				if (TYPE(ch) == argument && NCH(ch) == 2 &&
+				    TYPE(CHILD(ch, 1)) == gen_for) {
+					PyErr_SetString(PyExc_SyntaxError,
+							"invalid syntax");
+					symtable_error(st, n->n_lineno);
+					return;
+				}
+			}
 	/* The remaining cases fall through to default except in
 	   special circumstances.  This requires the individual cases
 	   to be coded with great care, even though they look like
@@ -5504,6 +5697,11 @@ symtable_node(struct symtable *st, node *n)
 			n = CHILD(n, 2);
 			goto loop;
 		}
+		else if (TYPE(n) == argument && NCH(n) == 2 &&
+			TYPE(CHILD(n, 1)) == gen_for) {
+			symtable_generator_expression(st, n);
+			break;
+		}
 		/* fall through */
 	case listmaker:
 		if (NCH(n) > 1 && TYPE(CHILD(n, 1)) == list_for) {
@@ -5511,6 +5709,13 @@ symtable_node(struct symtable *st, node *n)
 			break;
 		}
 		/* fall through */
+	case testlist_gexp:
+		if (NCH(n) > 1 && TYPE(CHILD(n, 1)) == gen_for) {
+			symtable_generator_expression(st, n); 
+			break;
+		}
+		/* fall through */
+
 	case atom:
 		if (TYPE(n) == atom && TYPE(CHILD(n, 0)) == NAME) {
 			symtable_add_use(st, STR(CHILD(n, 0)));
@@ -5715,6 +5920,26 @@ symtable_list_comprehension(struct symtable *st, node *n)
 }
 
 static void
+symtable_generator_expression(struct symtable *st, node *n)
+{
+	/* testlist_gexp: test gen_for */
+	REQ(CHILD(n, 0), test);
+	REQ(CHILD(n, 1), gen_for);
+
+	symtable_enter_scope(st, "<genexpr>", TYPE(n), n->n_lineno);
+	st->st_cur->ste_generator = GENERATOR_EXPRESSION;
+
+	symtable_add_def(st, "[outmost-iterable]", DEF_PARAM);
+	
+	symtable_gen_for(st, CHILD(n, 1), 1);
+	symtable_node(st, CHILD(n, 0));
+	symtable_exit_scope(st);
+
+	/* for outmost iterable precomputation */
+	symtable_node(st, CHILD(CHILD(n, 1), 3)); 
+}
+
+static void
 symtable_list_for(struct symtable *st, node *n)
 {
 	REQ(n, list_for);
@@ -5726,6 +5951,39 @@ symtable_list_for(struct symtable *st, node *n)
 }
 
 static void
+symtable_gen_for(struct symtable *st, node *n, int is_outmost)
+{
+	REQ(n, gen_for);
+
+	/* gen_for: for v in test [gen_iter] */
+	symtable_assign(st, CHILD(n, 1), 0);
+	if (is_outmost)
+		symtable_add_use(st, "[outmost-iterable]");
+	else
+		symtable_node(st, CHILD(n, 3));
+
+	if (NCH(n) == 5)
+		symtable_gen_iter(st, CHILD(n, 4));
+}
+
+static void
+symtable_gen_iter(struct symtable *st, node *n)
+{
+	REQ(n, gen_iter);
+
+	n = CHILD(n, 0);
+	if (TYPE(n) == gen_for)
+		symtable_gen_for(st, n, 0);
+	else {
+		REQ(n, gen_if);
+		symtable_node(st, CHILD(n, 1));
+
+		if (NCH(n) == 3)
+			symtable_gen_iter(st, CHILD(n, 2));
+	}
+}
+
+static void
 symtable_import(struct symtable *st, node *n)
 {
 	int i;
@@ -5813,6 +6071,17 @@ symtable_assign(struct symtable *st, node *n, int def_flag)
 				symtable_assign(st, CHILD(n, i), def_flag);
 		}
 		return;
+	case testlist_gexp:
+		if (NCH(n) > 1 && TYPE(CHILD(n, 1)) == gen_for) {
+			/* XXX This is an error, but the next pass
+			   will catch it. */ 
+			return;
+		} else {
+			for (i = 0; i < NCH(n); i += 2)
+				symtable_assign(st, CHILD(n, i), def_flag);
+		}
+		return;
+
 	case exprlist:
 	case testlist:
 	case testlist1:
diff --git a/Python/graminit.c b/Python/graminit.c
index 98bad94..cd8240b 100644
--- a/Python/graminit.c
+++ b/Python/graminit.c
@@ -1016,46 +1016,46 @@ static state states_48[4] = {
 };
 static arc arcs_49_0[7] = {
 	{16, 1},
-	{127, 2},
-	{130, 3},
-	{133, 4},
+	{128, 2},
+	{131, 3},
+	{134, 4},
 	{12, 5},
-	{135, 5},
-	{136, 6},
+	{136, 5},
+	{137, 6},
 };
 static arc arcs_49_1[2] = {
-	{9, 7},
+	{127, 7},
 	{18, 5},
 };
 static arc arcs_49_2[2] = {
-	{128, 8},
-	{129, 5},
+	{129, 8},
+	{130, 5},
 };
 static arc arcs_49_3[2] = {
-	{131, 9},
-	{132, 5},
+	{132, 9},
+	{133, 5},
 };
 static arc arcs_49_4[1] = {
-	{134, 10},
+	{135, 10},
 };
 static arc arcs_49_5[1] = {
 	{0, 5},
 };
 static arc arcs_49_6[2] = {
-	{136, 6},
+	{137, 6},
 	{0, 6},
 };
 static arc arcs_49_7[1] = {
 	{18, 5},
 };
 static arc arcs_49_8[1] = {
-	{129, 5},
+	{130, 5},
 };
 static arc arcs_49_9[1] = {
-	{132, 5},
+	{133, 5},
 };
 static arc arcs_49_10[1] = {
-	{133, 5},
+	{134, 5},
 };
 static state states_49[11] = {
 	{7, arcs_49_0},
@@ -1074,7 +1074,7 @@ static arc arcs_50_0[1] = {
 	{21, 1},
 };
 static arc arcs_50_1[3] = {
-	{137, 2},
+	{138, 2},
 	{22, 3},
 	{0, 1},
 };
@@ -1097,153 +1097,163 @@ static state states_50[5] = {
 	{2, arcs_50_4},
 };
 static arc arcs_51_0[1] = {
-	{138, 1},
+	{21, 1},
 };
-static arc arcs_51_1[2] = {
-	{17, 2},
-	{14, 3},
+static arc arcs_51_1[3] = {
+	{139, 2},
+	{22, 3},
+	{0, 1},
 };
 static arc arcs_51_2[1] = {
-	{14, 3},
+	{0, 2},
 };
-static arc arcs_51_3[1] = {
+static arc arcs_51_3[2] = {
 	{21, 4},
+	{0, 3},
 };
-static arc arcs_51_4[1] = {
+static arc arcs_51_4[2] = {
+	{22, 3},
 	{0, 4},
 };
 static state states_51[5] = {
 	{1, arcs_51_0},
-	{2, arcs_51_1},
+	{3, arcs_51_1},
 	{1, arcs_51_2},
-	{1, arcs_51_3},
-	{1, arcs_51_4},
+	{2, arcs_51_3},
+	{2, arcs_51_4},
 };
-static arc arcs_52_0[3] = {
-	{16, 1},
-	{127, 2},
-	{70, 3},
+static arc arcs_52_0[1] = {
+	{140, 1},
 };
 static arc arcs_52_1[2] = {
-	{139, 4},
-	{18, 5},
+	{17, 2},
+	{14, 3},
 };
 static arc arcs_52_2[1] = {
-	{140, 6},
+	{14, 3},
 };
 static arc arcs_52_3[1] = {
-	{12, 5},
+	{21, 4},
 };
 static arc arcs_52_4[1] = {
-	{18, 5},
-};
-static arc arcs_52_5[1] = {
-	{0, 5},
-};
-static arc arcs_52_6[1] = {
-	{129, 5},
+	{0, 4},
 };
-static state states_52[7] = {
-	{3, arcs_52_0},
+static state states_52[5] = {
+	{1, arcs_52_0},
 	{2, arcs_52_1},
 	{1, arcs_52_2},
 	{1, arcs_52_3},
 	{1, arcs_52_4},
-	{1, arcs_52_5},
-	{1, arcs_52_6},
 };
-static arc arcs_53_0[1] = {
-	{141, 1},
+static arc arcs_53_0[3] = {
+	{16, 1},
+	{128, 2},
+	{70, 3},
 };
 static arc arcs_53_1[2] = {
+	{141, 4},
+	{18, 5},
+};
+static arc arcs_53_2[1] = {
+	{142, 6},
+};
+static arc arcs_53_3[1] = {
+	{12, 5},
+};
+static arc arcs_53_4[1] = {
+	{18, 5},
+};
+static arc arcs_53_5[1] = {
+	{0, 5},
+};
+static arc arcs_53_6[1] = {
+	{130, 5},
+};
+static state states_53[7] = {
+	{3, arcs_53_0},
+	{2, arcs_53_1},
+	{1, arcs_53_2},
+	{1, arcs_53_3},
+	{1, arcs_53_4},
+	{1, arcs_53_5},
+	{1, arcs_53_6},
+};
+static arc arcs_54_0[1] = {
+	{143, 1},
+};
+static arc arcs_54_1[2] = {
 	{22, 2},
 	{0, 1},
 };
-static arc arcs_53_2[2] = {
-	{141, 1},
+static arc arcs_54_2[2] = {
+	{143, 1},
 	{0, 2},
 };
-static state states_53[3] = {
-	{1, arcs_53_0},
-	{2, arcs_53_1},
-	{2, arcs_53_2},
+static state states_54[3] = {
+	{1, arcs_54_0},
+	{2, arcs_54_1},
+	{2, arcs_54_2},
 };
-static arc arcs_54_0[3] = {
+static arc arcs_55_0[3] = {
 	{70, 1},
 	{21, 2},
 	{14, 3},
 };
-static arc arcs_54_1[1] = {
+static arc arcs_55_1[1] = {
 	{70, 4},
 };
-static arc arcs_54_2[2] = {
+static arc arcs_55_2[2] = {
 	{14, 3},
 	{0, 2},
 };
-static arc arcs_54_3[3] = {
+static arc arcs_55_3[3] = {
 	{21, 5},
-	{142, 6},
+	{144, 6},
 	{0, 3},
 };
-static arc arcs_54_4[1] = {
+static arc arcs_55_4[1] = {
 	{70, 6},
 };
-static arc arcs_54_5[2] = {
-	{142, 6},
+static arc arcs_55_5[2] = {
+	{144, 6},
 	{0, 5},
 };
-static arc arcs_54_6[1] = {
+static arc arcs_55_6[1] = {
 	{0, 6},
 };
-static state states_54[7] = {
-	{3, arcs_54_0},
-	{1, arcs_54_1},
-	{2, arcs_54_2},
-	{3, arcs_54_3},
-	{1, arcs_54_4},
-	{2, arcs_54_5},
-	{1, arcs_54_6},
-};
-static arc arcs_55_0[1] = {
-	{14, 1},
-};
-static arc arcs_55_1[2] = {
-	{21, 2},
-	{0, 1},
-};
-static arc arcs_55_2[1] = {
-	{0, 2},
-};
-static state states_55[3] = {
-	{1, arcs_55_0},
-	{2, arcs_55_1},
-	{1, arcs_55_2},
+static state states_55[7] = {
+	{3, arcs_55_0},
+	{1, arcs_55_1},
+	{2, arcs_55_2},
+	{3, arcs_55_3},
+	{1, arcs_55_4},
+	{2, arcs_55_5},
+	{1, arcs_55_6},
 };
 static arc arcs_56_0[1] = {
-	{73, 1},
+	{14, 1},
 };
 static arc arcs_56_1[2] = {
-	{22, 2},
+	{21, 2},
 	{0, 1},
 };
-static arc arcs_56_2[2] = {
-	{73, 1},
+static arc arcs_56_2[1] = {
 	{0, 2},
 };
 static state states_56[3] = {
 	{1, arcs_56_0},
 	{2, arcs_56_1},
-	{2, arcs_56_2},
+	{1, arcs_56_2},
 };
 static arc arcs_57_0[1] = {
-	{21, 1},
+	{73, 1},
 };
 static arc arcs_57_1[2] = {
 	{22, 2},
 	{0, 1},
 };
 static arc arcs_57_2[2] = {
-	{21, 1},
+	{73, 1},
 	{0, 2},
 };
 static state states_57[3] = {
@@ -1258,29 +1268,21 @@ static arc arcs_58_1[2] = {
 	{22, 2},
 	{0, 1},
 };
-static arc arcs_58_2[1] = {
-	{21, 3},
-};
-static arc arcs_58_3[2] = {
-	{22, 4},
-	{0, 3},
-};
-static arc arcs_58_4[2] = {
-	{21, 3},
-	{0, 4},
+static arc arcs_58_2[2] = {
+	{21, 1},
+	{0, 2},
 };
-static state states_58[5] = {
+static state states_58[3] = {
 	{1, arcs_58_0},
 	{2, arcs_58_1},
-	{1, arcs_58_2},
-	{2, arcs_58_3},
-	{2, arcs_58_4},
+	{2, arcs_58_2},
 };
 static arc arcs_59_0[1] = {
 	{21, 1},
 };
-static arc arcs_59_1[1] = {
-	{14, 2},
+static arc arcs_59_1[2] = {
+	{22, 2},
+	{0, 1},
 };
 static arc arcs_59_2[1] = {
 	{21, 3},
@@ -1290,328 +1292,423 @@ static arc arcs_59_3[2] = {
 	{0, 3},
 };
 static arc arcs_59_4[2] = {
-	{21, 1},
+	{21, 3},
 	{0, 4},
 };
 static state states_59[5] = {
 	{1, arcs_59_0},
-	{1, arcs_59_1},
+	{2, arcs_59_1},
 	{1, arcs_59_2},
 	{2, arcs_59_3},
 	{2, arcs_59_4},
 };
 static arc arcs_60_0[1] = {
-	{144, 1},
+	{21, 1},
 };
 static arc arcs_60_1[1] = {
+	{14, 2},
+};
+static arc arcs_60_2[1] = {
+	{21, 3},
+};
+static arc arcs_60_3[2] = {
+	{22, 4},
+	{0, 3},
+};
+static arc arcs_60_4[2] = {
+	{21, 1},
+	{0, 4},
+};
+static state states_60[5] = {
+	{1, arcs_60_0},
+	{1, arcs_60_1},
+	{1, arcs_60_2},
+	{2, arcs_60_3},
+	{2, arcs_60_4},
+};
+static arc arcs_61_0[1] = {
+	{146, 1},
+};
+static arc arcs_61_1[1] = {
 	{12, 2},
 };
-static arc arcs_60_2[2] = {
+static arc arcs_61_2[2] = {
 	{16, 3},
 	{14, 4},
 };
-static arc arcs_60_3[1] = {
+static arc arcs_61_3[1] = {
 	{9, 5},
 };
-static arc arcs_60_4[1] = {
+static arc arcs_61_4[1] = {
 	{15, 6},
 };
-static arc arcs_60_5[1] = {
+static arc arcs_61_5[1] = {
 	{18, 7},
 };
-static arc arcs_60_6[1] = {
+static arc arcs_61_6[1] = {
 	{0, 6},
 };
-static arc arcs_60_7[1] = {
+static arc arcs_61_7[1] = {
 	{14, 4},
 };
-static state states_60[8] = {
-	{1, arcs_60_0},
-	{1, arcs_60_1},
-	{2, arcs_60_2},
-	{1, arcs_60_3},
-	{1, arcs_60_4},
-	{1, arcs_60_5},
-	{1, arcs_60_6},
-	{1, arcs_60_7},
-};
-static arc arcs_61_0[3] = {
-	{145, 1},
+static state states_61[8] = {
+	{1, arcs_61_0},
+	{1, arcs_61_1},
+	{2, arcs_61_2},
+	{1, arcs_61_3},
+	{1, arcs_61_4},
+	{1, arcs_61_5},
+	{1, arcs_61_6},
+	{1, arcs_61_7},
+};
+static arc arcs_62_0[3] = {
+	{147, 1},
 	{23, 2},
 	{24, 3},
 };
-static arc arcs_61_1[2] = {
+static arc arcs_62_1[2] = {
 	{22, 4},
 	{0, 1},
 };
-static arc arcs_61_2[1] = {
+static arc arcs_62_2[1] = {
 	{21, 5},
 };
-static arc arcs_61_3[1] = {
+static arc arcs_62_3[1] = {
 	{21, 6},
 };
-static arc arcs_61_4[4] = {
-	{145, 1},
+static arc arcs_62_4[4] = {
+	{147, 1},
 	{23, 2},
 	{24, 3},
 	{0, 4},
 };
-static arc arcs_61_5[2] = {
+static arc arcs_62_5[2] = {
 	{22, 7},
 	{0, 5},
 };
-static arc arcs_61_6[1] = {
+static arc arcs_62_6[1] = {
 	{0, 6},
 };
-static arc arcs_61_7[1] = {
+static arc arcs_62_7[1] = {
 	{24, 3},
 };
-static state states_61[8] = {
-	{3, arcs_61_0},
-	{2, arcs_61_1},
-	{1, arcs_61_2},
-	{1, arcs_61_3},
-	{4, arcs_61_4},
-	{2, arcs_61_5},
-	{1, arcs_61_6},
-	{1, arcs_61_7},
+static state states_62[8] = {
+	{3, arcs_62_0},
+	{2, arcs_62_1},
+	{1, arcs_62_2},
+	{1, arcs_62_3},
+	{4, arcs_62_4},
+	{2, arcs_62_5},
+	{1, arcs_62_6},
+	{1, arcs_62_7},
 };
-static arc arcs_62_0[1] = {
+static arc arcs_63_0[1] = {
 	{21, 1},
 };
-static arc arcs_62_1[2] = {
+static arc arcs_63_1[3] = {
 	{20, 2},
+	{139, 3},
 	{0, 1},
 };
-static arc arcs_62_2[1] = {
-	{21, 3},
+static arc arcs_63_2[1] = {
+	{21, 4},
 };
-static arc arcs_62_3[1] = {
+static arc arcs_63_3[1] = {
 	{0, 3},
 };
-static state states_62[4] = {
-	{1, arcs_62_0},
-	{2, arcs_62_1},
-	{1, arcs_62_2},
-	{1, arcs_62_3},
+static arc arcs_63_4[2] = {
+	{139, 3},
+	{0, 4},
 };
-static arc arcs_63_0[2] = {
-	{137, 1},
-	{147, 1},
+static state states_63[5] = {
+	{1, arcs_63_0},
+	{3, arcs_63_1},
+	{1, arcs_63_2},
+	{1, arcs_63_3},
+	{2, arcs_63_4},
+};
+static arc arcs_64_0[2] = {
+	{138, 1},
+	{149, 1},
 };
-static arc arcs_63_1[1] = {
+static arc arcs_64_1[1] = {
 	{0, 1},
 };
-static state states_63[2] = {
-	{2, arcs_63_0},
-	{1, arcs_63_1},
+static state states_64[2] = {
+	{2, arcs_64_0},
+	{1, arcs_64_1},
 };
-static arc arcs_64_0[1] = {
+static arc arcs_65_0[1] = {
 	{85, 1},
 };
-static arc arcs_64_1[1] = {
+static arc arcs_65_1[1] = {
 	{53, 2},
 };
-static arc arcs_64_2[1] = {
+static arc arcs_65_2[1] = {
 	{74, 3},
 };
-static arc arcs_64_3[1] = {
-	{143, 4},
+static arc arcs_65_3[1] = {
+	{145, 4},
 };
-static arc arcs_64_4[2] = {
-	{146, 5},
+static arc arcs_65_4[2] = {
+	{148, 5},
 	{0, 4},
 };
-static arc arcs_64_5[1] = {
+static arc arcs_65_5[1] = {
 	{0, 5},
 };
-static state states_64[6] = {
-	{1, arcs_64_0},
-	{1, arcs_64_1},
-	{1, arcs_64_2},
-	{1, arcs_64_3},
-	{2, arcs_64_4},
-	{1, arcs_64_5},
+static state states_65[6] = {
+	{1, arcs_65_0},
+	{1, arcs_65_1},
+	{1, arcs_65_2},
+	{1, arcs_65_3},
+	{2, arcs_65_4},
+	{1, arcs_65_5},
 };
-static arc arcs_65_0[1] = {
+static arc arcs_66_0[1] = {
 	{81, 1},
 };
-static arc arcs_65_1[1] = {
+static arc arcs_66_1[1] = {
 	{21, 2},
 };
-static arc arcs_65_2[2] = {
-	{146, 3},
+static arc arcs_66_2[2] = {
+	{148, 3},
 	{0, 2},
 };
-static arc arcs_65_3[1] = {
+static arc arcs_66_3[1] = {
 	{0, 3},
 };
-static state states_65[4] = {
-	{1, arcs_65_0},
-	{1, arcs_65_1},
-	{2, arcs_65_2},
-	{1, arcs_65_3},
+static state states_66[4] = {
+	{1, arcs_66_0},
+	{1, arcs_66_1},
+	{2, arcs_66_2},
+	{1, arcs_66_3},
 };
-static arc arcs_66_0[1] = {
+static arc arcs_67_0[2] = {
+	{139, 1},
+	{151, 1},
+};
+static arc arcs_67_1[1] = {
+	{0, 1},
+};
+static state states_67[2] = {
+	{2, arcs_67_0},
+	{1, arcs_67_1},
+};
+static arc arcs_68_0[1] = {
+	{85, 1},
+};
+static arc arcs_68_1[1] = {
+	{53, 2},
+};
+static arc arcs_68_2[1] = {
+	{74, 3},
+};
+static arc arcs_68_3[1] = {
+	{21, 4},
+};
+static arc arcs_68_4[2] = {
+	{150, 5},
+	{0, 4},
+};
+static arc arcs_68_5[1] = {
+	{0, 5},
+};
+static state states_68[6] = {
+	{1, arcs_68_0},
+	{1, arcs_68_1},
+	{1, arcs_68_2},
+	{1, arcs_68_3},
+	{2, arcs_68_4},
+	{1, arcs_68_5},
+};
+static arc arcs_69_0[1] = {
+	{81, 1},
+};
+static arc arcs_69_1[1] = {
+	{21, 2},
+};
+static arc arcs_69_2[2] = {
+	{150, 3},
+	{0, 2},
+};
+static arc arcs_69_3[1] = {
+	{0, 3},
+};
+static state states_69[4] = {
+	{1, arcs_69_0},
+	{1, arcs_69_1},
+	{2, arcs_69_2},
+	{1, arcs_69_3},
+};
+static arc arcs_70_0[1] = {
 	{21, 1},
 };
-static arc arcs_66_1[2] = {
+static arc arcs_70_1[2] = {
 	{22, 0},
 	{0, 1},
 };
-static state states_66[2] = {
-	{1, arcs_66_0},
-	{2, arcs_66_1},
+static state states_70[2] = {
+	{1, arcs_70_0},
+	{2, arcs_70_1},
 };
-static arc arcs_67_0[1] = {
+static arc arcs_71_0[1] = {
 	{12, 1},
 };
-static arc arcs_67_1[1] = {
+static arc arcs_71_1[1] = {
 	{0, 1},
 };
-static state states_67[2] = {
-	{1, arcs_67_0},
-	{1, arcs_67_1},
+static state states_71[2] = {
+	{1, arcs_71_0},
+	{1, arcs_71_1},
 };
-static dfa dfas[68] = {
+static dfa dfas[72] = {
 	{256, "single_input", 0, 3, states_0,
-	 "\004\030\001\000\000\000\124\360\213\011\162\000\002\000\140\210\244\005\001"},
+	 "\004\030\001\000\000\000\124\360\213\011\162\000\002\000\140\010\111\023\004\000"},
 	{257, "file_input", 0, 2, states_1,
-	 "\204\030\001\000\000\000\124\360\213\011\162\000\002\000\140\210\244\005\001"},
+	 "\204\030\001\000\000\000\124\360\213\011\162\000\002\000\140\010\111\023\004\000"},
 	{258, "eval_input", 0, 3, states_2,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
 	{259, "funcdef", 0, 6, states_3,
-	 "\000\010\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\010\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{260, "parameters", 0, 4, states_4,
-	 "\000\000\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{261, "varargslist", 0, 10, states_5,
-	 "\000\020\201\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\020\201\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{262, "fpdef", 0, 4, states_6,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{263, "fplist", 0, 3, states_7,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{264, "stmt", 0, 2, states_8,
-	 "\000\030\001\000\000\000\124\360\213\011\162\000\002\000\140\210\244\005\001"},
+	 "\000\030\001\000\000\000\124\360\213\011\162\000\002\000\140\010\111\023\004\000"},
 	{265, "simple_stmt", 0, 4, states_9,
-	 "\000\020\001\000\000\000\124\360\213\011\000\000\002\000\140\210\244\005\000"},
+	 "\000\020\001\000\000\000\124\360\213\011\000\000\002\000\140\010\111\023\000\000"},
 	{266, "small_stmt", 0, 2, states_10,
-	 "\000\020\001\000\000\000\124\360\213\011\000\000\002\000\140\210\244\005\000"},
+	 "\000\020\001\000\000\000\124\360\213\011\000\000\002\000\140\010\111\023\000\000"},
 	{267, "expr_stmt", 0, 6, states_11,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
 	{268, "augassign", 0, 2, states_12,
-	 "\000\000\000\000\300\377\003\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\300\377\003\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{269, "print_stmt", 0, 9, states_13,
-	 "\000\000\000\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{270, "del_stmt", 0, 3, states_14,
-	 "\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{271, "pass_stmt", 0, 2, states_15,
-	 "\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{272, "flow_stmt", 0, 2, states_16,
-	 "\000\000\000\000\000\000\000\360\001\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\360\001\000\000\000\000\000\000\000\000\000\000\000"},
 	{273, "break_stmt", 0, 2, states_17,
-	 "\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{274, "continue_stmt", 0, 2, states_18,
-	 "\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{275, "return_stmt", 0, 3, states_19,
-	 "\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{276, "yield_stmt", 0, 3, states_20,
-	 "\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{277, "raise_stmt", 0, 7, states_21,
-	 "\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000\000\000"},
 	{278, "import_stmt", 0, 9, states_22,
-	 "\000\000\000\000\000\000\000\000\012\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\012\000\000\000\000\000\000\000\000\000\000\000"},
 	{279, "import_as_name", 0, 4, states_23,
-	 "\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{280, "dotted_as_name", 0, 4, states_24,
-	 "\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{281, "dotted_name", 0, 2, states_25,
-	 "\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
 	{282, "global_stmt", 0, 3, states_26,
-	 "\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000"},
 	{283, "exec_stmt", 0, 7, states_27,
-	 "\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000\000"},
 	{284, "assert_stmt", 0, 5, states_28,
-	 "\000\000\000\000\000\000\000\000\000\010\000\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\000\010\000\000\000\000\000\000\000\000\000\000"},
 	{285, "compound_stmt", 0, 2, states_29,
-	 "\000\010\000\000\000\000\000\000\000\000\162\000\000\000\000\000\000\000\001"},
+	 "\000\010\000\000\000\000\000\000\000\000\162\000\000\000\000\000\000\000\004\000"},
 	{286, "if_stmt", 0, 8, states_30,
-	 "\000\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000\000\000"},
 	{287, "while_stmt", 0, 8, states_31,
-	 "\000\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000"},
 	{288, "for_stmt", 0, 10, states_32,
-	 "\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000"},
 	{289, "try_stmt", 0, 10, states_33,
-	 "\000\000\000\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000"},
 	{290, "except_clause", 0, 5, states_34,
-	 "\000\000\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000\000"},
 	{291, "suite", 0, 5, states_35,
-	 "\004\020\001\000\000\000\124\360\213\011\000\000\002\000\140\210\244\005\000"},
+	 "\004\020\001\000\000\000\124\360\213\011\000\000\002\000\140\010\111\023\000\000"},
 	{292, "test", 0, 4, states_36,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
 	{293, "and_test", 0, 2, states_37,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\003\000\000"},
 	{294, "not_test", 0, 3, states_38,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\003\000\000"},
 	{295, "comparison", 0, 2, states_39,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
 	{296, "comp_op", 0, 4, states_40,
-	 "\000\000\000\000\000\000\000\000\000\004\000\000\362\017\000\000\000\000\000"},
+	 "\000\000\000\000\000\000\000\000\000\004\000\000\362\017\000\000\000\000\000\000"},
 	{297, "expr", 0, 2, states_41,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
 	{298, "xor_expr", 0, 2, states_42,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
 	{299, "and_expr", 0, 2, states_43,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
 	{300, "shift_expr", 0, 2, states_44,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
 	{301, "arith_expr", 0, 2, states_45,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
 	{302, "term", 0, 2, states_46,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
 	{303, "factor", 0, 3, states_47,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
 	{304, "power", 0, 4, states_48,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\000\200\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\000\000\111\003\000\000"},
 	{305, "atom", 0, 11, states_49,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\000\200\244\001\000"},
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\000\000\111\003\000\000"},
 	{306, "listmaker", 0, 5, states_50,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
-	{307, "lambdef", 0, 5, states_51,
-	 "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\004\000"},
-	{308, "trailer", 0, 7, states_52,
-	 "\000\000\001\000\000\000\000\000\100\000\000\000\000\000\000\200\000\000\000"},
-	{309, "subscriptlist", 0, 3, states_53,
-	 "\000\120\001\000\000\000\000\000\100\000\000\000\002\000\140\210\244\005\000"},
-	{310, "subscript", 0, 7, states_54,
-	 "\000\120\001\000\000\000\000\000\100\000\000\000\002\000\140\210\244\005\000"},
-	{311, "sliceop", 0, 3, states_55,
-	 "\000\100\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-	{312, "exprlist", 0, 3, states_56,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\210\244\001\000"},
-	{313, "testlist", 0, 3, states_57,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
-	{314, "testlist_safe", 0, 5, states_58,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
-	{315, "dictmaker", 0, 5, states_59,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
-	{316, "classdef", 0, 8, states_60,
-	 "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\001"},
-	{317, "arglist", 0, 8, states_61,
-	 "\000\020\201\001\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
-	{318, "argument", 0, 4, states_62,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
-	{319, "list_iter", 0, 2, states_63,
-	 "\000\000\000\000\000\000\000\000\000\000\042\000\000\000\000\000\000\000\000"},
-	{320, "list_for", 0, 6, states_64,
-	 "\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000"},
-	{321, "list_if", 0, 4, states_65,
-	 "\000\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000\000"},
-	{322, "testlist1", 0, 2, states_66,
-	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\210\244\005\000"},
-	{323, "encoding_decl", 0, 2, states_67,
-	 "\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-};
-static label labels[149] = {
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
+	{307, "testlist_gexp", 0, 5, states_51,
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
+	{308, "lambdef", 0, 5, states_52,
+	 "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\020\000\000"},
+	{309, "trailer", 0, 7, states_53,
+	 "\000\000\001\000\000\000\000\000\100\000\000\000\000\000\000\000\001\000\000\000"},
+	{310, "subscriptlist", 0, 3, states_54,
+	 "\000\120\001\000\000\000\000\000\100\000\000\000\002\000\140\010\111\023\000\000"},
+	{311, "subscript", 0, 7, states_55,
+	 "\000\120\001\000\000\000\000\000\100\000\000\000\002\000\140\010\111\023\000\000"},
+	{312, "sliceop", 0, 3, states_56,
+	 "\000\100\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+	{313, "exprlist", 0, 3, states_57,
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\000\000\140\010\111\003\000\000"},
+	{314, "testlist", 0, 3, states_58,
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
+	{315, "testlist_safe", 0, 5, states_59,
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
+	{316, "dictmaker", 0, 5, states_60,
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
+	{317, "classdef", 0, 8, states_61,
+	 "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\004\000"},
+	{318, "arglist", 0, 8, states_62,
+	 "\000\020\201\001\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
+	{319, "argument", 0, 5, states_63,
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
+	{320, "list_iter", 0, 2, states_64,
+	 "\000\000\000\000\000\000\000\000\000\000\042\000\000\000\000\000\000\000\000\000"},
+	{321, "list_for", 0, 6, states_65,
+	 "\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000"},
+	{322, "list_if", 0, 4, states_66,
+	 "\000\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000\000\000"},
+	{323, "gen_iter", 0, 2, states_67,
+	 "\000\000\000\000\000\000\000\000\000\000\042\000\000\000\000\000\000\000\000\000"},
+	{324, "gen_for", 0, 6, states_68,
+	 "\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000"},
+	{325, "gen_if", 0, 4, states_69,
+	 "\000\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000\000\000"},
+	{326, "testlist1", 0, 2, states_70,
+	 "\000\020\001\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
+	{327, "encoding_decl", 0, 2, states_71,
+	 "\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+};
+static label labels[153] = {
 	{0, "EMPTY"},
 	{256, 0},
 	{4, 0},
@@ -1621,7 +1718,7 @@ static label labels[149] = {
 	{264, 0},
 	{0, 0},
 	{258, 0},
-	{313, 0},
+	{314, 0},
 	{259, 0},
 	{1, "def"},
 	{1, 0},
@@ -1665,7 +1762,7 @@ static label labels[149] = {
 	{1, "print"},
 	{35, 0},
 	{1, "del"},
-	{312, 0},
+	{313, 0},
 	{1, "pass"},
 	{273, 0},
 	{274, 0},
@@ -1692,7 +1789,7 @@ static label labels[149] = {
 	{287, 0},
 	{288, 0},
 	{289, 0},
-	{316, 0},
+	{317, 0},
 	{1, "if"},
 	{1, "elif"},
 	{1, "else"},
@@ -1706,7 +1803,7 @@ static label labels[149] = {
 	{6, 0},
 	{293, 0},
 	{1, "or"},
-	{307, 0},
+	{308, 0},
 	{294, 0},
 	{1, "and"},
 	{1, "not"},
@@ -1738,33 +1835,37 @@ static label labels[149] = {
 	{32, 0},
 	{304, 0},
 	{305, 0},
-	{308, 0},
+	{309, 0},
+	{307, 0},
 	{9, 0},
 	{306, 0},
 	{10, 0},
 	{26, 0},
-	{315, 0},
+	{316, 0},
 	{27, 0},
 	{25, 0},
-	{322, 0},
+	{326, 0},
 	{2, 0},
 	{3, 0},
-	{320, 0},
+	{321, 0},
+	{324, 0},
 	{1, "lambda"},
-	{317, 0},
-	{309, 0},
+	{318, 0},
 	{310, 0},
 	{311, 0},
-	{314, 0},
+	{312, 0},
+	{315, 0},
 	{1, "class"},
-	{318, 0},
 	{319, 0},
-	{321, 0},
+	{320, 0},
+	{322, 0},
 	{323, 0},
+	{325, 0},
+	{327, 0},
 };
 grammar _PyParser_Grammar = {
-	68,
+	72,
 	dfas,
-	{149, labels},
+	{153, labels},
 	256
 };
diff --git a/Python/symtable.c b/Python/symtable.c
index f86fd2f..5ca2041 100644
--- a/Python/symtable.c
+++ b/Python/symtable.c
@@ -66,6 +66,8 @@ PySymtableEntry_New(struct symtable *st, char *name, int type, int lineno)
 	switch (type) {
 	case funcdef:
 	case lambdef:
+	case testlist_gexp: /* generator expression */
+	case argument:      /* generator expression */
 		ste->ste_type = TYPE_FUNCTION;
 		break;
 	case classdef:
diff --git a/Tools/compiler/ast.txt b/Tools/compiler/ast.txt
index 3f8953b..6a990d4 100644
--- a/Tools/compiler/ast.txt
+++ b/Tools/compiler/ast.txt
@@ -38,6 +38,10 @@ AssAttr: expr, attrname*, flags*
 ListComp: expr, quals!
 ListCompFor: assign, list, ifs!
 ListCompIf: test
+GenExpr: code 
+GenExprInner: expr, quals!
+GenExprFor: assign, iter, ifs!
+GenExprIf: test
 List: nodes!
 Dict: items!
 Not: expr
@@ -85,3 +89,10 @@ init(Lambda):
         self.varargs = 1
     if flags & CO_VARKEYWORDS:
         self.kwargs = 1
+
+init(GenExpr):
+    self.argnames = ['[outmost-iterable]']
+    self.varargs = self.kwargs = None
+
+init(GenExprFor):
+    self.is_outmost = False