merge

Cython/Compiler/ExprNodes.py

@@ -3719,7 +3719,6 @@ class DictNode(ExprNode):
     is_temp = 1
     type = dict_type
 
-    type = dict_type
     obj_conversion_errors = []
 
     def calculate_constant_result(self):

Cython/Compiler/Main.py

@@ -93,6 +93,7 @@ class Context(object):
         from AutoDocTransforms import EmbedSignature
         from Optimize import FlattenInListTransform, SwitchTransform, IterationTransform
         from Optimize import OptimizeBuiltinCalls, ConstantFolding, FinalOptimizePhase
+        from Optimize import DropRefcountingTransform
         from Buffer import IntroduceBufferAuxiliaryVars
         from ModuleNode import check_c_declarations, check_c_declarations_pxd
 
@@ -138,6 +139,7 @@ class Context(object):
             OptimizeBuiltinCalls(),
             IterationTransform(),
             SwitchTransform(),
+            DropRefcountingTransform(),
             FinalOptimizePhase(self),
             GilCheck(),
 #            ClearResultCodes(self),

Cython/Compiler/Optimize.py

@@ -528,39 +528,106 @@ class DropRefcountingTransform(Visitor.VisitorTransform):
     visit_Node = Visitor.VisitorTransform.recurse_to_children
 
     def visit_ParallelAssignmentNode(self, node):
-        left, right, temps = [], [], []
+        left_names, right_names = [], []
+        left_indices, right_indices = [], []
+        temps = []
+
         for stat in node.stats:
             if isinstance(stat, Nodes.SingleAssignmentNode):
-                lhs = unwrap_node(stat.lhs)
-                if not isinstance(lhs, ExprNodes.NameNode):
+                if not self._extract_operand(stat.lhs, left_names,
+                                             left_indices, temps):
+                    return node
+                if not self._extract_operand(stat.rhs, right_names,
+                                             right_indices, temps):
                     return node
-                left.append(lhs)
-                rhs = unwrap_node(stat.rhs)
-                if isinstance(rhs, ExprNodes.CoerceToTempNode):
-                    temps.append(rhs)
-                    rhs = rhs.arg
-                if not isinstance(rhs, ExprNodes.NameNode):
+            elif isinstance(stat, Nodes.CascadedAssignmentNode):
+                # FIXME
                 return node
-                right.append(rhs)
             else:
                 return node
 
-        for name_node in left + right:
-            if name_node.entry.is_builtin or name_node.entry.is_pyglobal:
+        if left_names or right_names:
+            # lhs/rhs names must be a non-redundant permutation
+            lnames = [n.name for n in left_names]
+            rnames = [n.name for n in right_names]
+            if set(lnames) != set(rnames):
+                return node
+            if len(set(lnames)) != len(right_names):
                 return node
 
-        left_names = [n.name for n in left]
-        right_names = [n.name for n in right]
-        if set(left_names) != set(right_names):
+        if left_indices or right_indices:
+            # base name and index of index nodes must be a
+            # non-redundant permutation
+            lindices = []
+            for lhs_node in left_indices:
+                index_id = self._extract_index_id(lhs_node)
+                if not index_id:
                     return node
-        if len(set(left_names)) != len(right):
+                lindices.append(index_id)
+            rindices = []
+            for rhs_node in right_indices:
+                index_id = self._extract_index_id(rhs_node)
+                if not index_id:
                     return node
+                rindices.append(index_id)
             
-        for name_node in left + right + temps:
+            if set(lindices) != set(rindices):
+                return node
+            if len(set(lindices)) != len(right_indices):
+                return node
+
+            # really supporting IndexNode requires support in
+            # __Pyx_GetItemInt(), so let's stop short for now
+            return node
+
+        temp_args = [t.arg for t in temps]
+        for temp in temps:
+            temp.use_managed_ref = False
+
+        for name_node in left_names + right_names:
+            if name_node not in temp_args:
                 name_node.use_managed_ref = False
 
+        for index_node in left_indices + right_indices:
+            index_node.use_managed_ref = False
+
         return node
 
+    def _extract_operand(self, node, names, indices, temps):
+        node = unwrap_node(node)
+        if not node.type.is_pyobject:
+            return False
+        if isinstance(node, ExprNodes.CoerceToTempNode):
+            temps.append(node)
+            node = node.arg
+        if isinstance(node, ExprNodes.NameNode):
+            if node.entry.is_builtin or node.entry.is_pyglobal:
+                return False
+            names.append(node)
+        elif isinstance(node, ExprNodes.IndexNode):
+            if node.base.type != Builtin.list_type:
+                return False
+            if not node.index.type.is_int:
+                return False
+            if not isinstance(node.base, ExprNodes.NameNode):
+                return False
+            indices.append(node)
+        else:
+            return False
+        return True
+
+    def _extract_index_id(self, index_node):
+        base = index_node.base
+        index = index_node.index
+        if isinstance(index, ExprNodes.NameNode):
+            index_val = index.name
+        elif isinstance(index, ExprNodes.ConstNode):
+            # FIXME:
+            return None
+        else:
+            return None
+        return (base.name, index_val)
+
 
 class OptimizeBuiltinCalls(Visitor.VisitorTransform):
     """Optimize some common methods calls and instantiation patterns

Cython/Compiler/ParseTreeTransforms.py

@@ -957,6 +957,7 @@ class TransformBuiltinMethods(EnvTransform):
             return node
     
     def visit_AttributeNode(self, node):
+        self.visitchildren(node)
         return self.visit_cython_attribute(node)
 
     def visit_NameNode(self, node):
@@ -978,8 +979,15 @@ class TransformBuiltinMethods(EnvTransform):
         # locals builtin
         if isinstance(node.function, ExprNodes.NameNode):
             if node.function.name == 'locals':
-                pos = node.pos
                 lenv = self.env_stack[-1]
+                entry = lenv.lookup_here('locals')
+                if entry:
+                    # not the builtin 'locals'
+                    return node
+                if len(node.args) > 0:
+                    error(self.pos, "Builtin 'locals()' called with wrong number of args, expected 0, got %d" % len(node.args))
+                    return node
+                pos = node.pos
                 items = [ExprNodes.DictItemNode(pos, 
                                                 key=ExprNodes.StringNode(pos, value=var),
                                                 value=ExprNodes.NameNode(pos, name=var)) for var in lenv.entries]

Tools/site_scons/site_tools/cython.py

+"""
+Tool to run Cython files (.pyx) into .c and .cpp.
+
+TODO:
+ - Add support for dynamically selecting in-process Cython
+   through CYTHONINPROCESS variable.
+ - Have a CYTHONCPP option which turns on C++ in flags and
+   changes output extension at the same time
+
+VARIABLES:
+ - CYTHON - The path to the "cython" command line tool.
+ - CYTHONFLAGS - Flags to pass to the "cython" command line tool.
+
+AUTHORS:
+ - David Cournapeau
+ - Dag Sverre Seljebotn
+
+"""
+import SCons
+from SCons.Builder import Builder
+from SCons.Action import Action
+
+#def cython_action(target, source, env):
+#    print target, source, env
+#    from Cython.Compiler.Main import compile as cython_compile
+#    res = cython_compile(str(source[0]))
+
+cythonAction = Action("$CYTHONCOM")
+
+def create_builder(env):
+    try:
+        cython = env['BUILDERS']['Cython']
+    except KeyError:
+        cython = SCons.Builder.Builder(
+                  action = cythonAction,
+                  emitter = {},
+                  suffix = cython_suffix_emitter,
+                  single_source = 1)
+        env['BUILDERS']['Cython'] = cython
+
+    return cython
+
+def cython_suffix_emitter(env, source):
+    print 'emitter called'
+    return "$CYTHONCFILESUFFIX"
+
+def generate(env):
+    env["CYTHON"] = "cython"
+    env["CYTHONCOM"] = "$CYTHON $CYTHONFLAGS -o $TARGET $SOURCE"
+    env["CYTHONCFILESUFFIX"] = ".c"
+
+    c_file, cxx_file = SCons.Tool.createCFileBuilders(env)
+
+    c_file.suffix['.pyx'] = cython_suffix_emitter
+    c_file.add_action('.pyx', cythonAction)
+
+    c_file.suffix['.py'] = cython_suffix_emitter
+    c_file.add_action('.py', cythonAction)
+
+    create_builder(env)
+
+def exists(env):
+    try:
+#        import Cython
+        return True
+    except ImportError:
+        return False

Tools/site_scons/site_tools/pyext.py

+"""SCons.Tool.pyext
+
+Tool-specific initialization for python extensions builder.
+
+AUTHORS:
+ - David Cournapeau
+ - Dag Sverre Seljebotn
+
+"""
+
+#
+# __COPYRIGHT__
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+#
+
+__revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
+
+import sys
+
+import SCons
+from SCons.Tool import SourceFileScanner, ProgramScanner
+
+#  Create common python builders
+
+def createPythonObjectBuilder(env):
+    """This is a utility function that creates the PythonObject Builder in an
+    Environment if it is not there already.
+
+    If it is already there, we return the existing one.
+    """
+
+    try:
+        pyobj = env['BUILDERS']['PythonObject']
+    except KeyError:
+        pyobj = SCons.Builder.Builder(action = {},
+                                      emitter = {},
+                                      prefix = '$PYEXTOBJPREFIX',
+                                      suffix = '$PYEXTOBJSUFFIX',
+                                      src_builder = ['CFile', 'CXXFile'],
+                                      source_scanner = SourceFileScanner,
+                                      single_source = 1)
+        env['BUILDERS']['PythonObject'] = pyobj
+
+    return pyobj
+
+def createPythonExtensionBuilder(env):
+    """This is a utility function that creates the PythonExtension Builder in
+    an Environment if it is not there already.
+
+    If it is already there, we return the existing one.
+    """
+
+    try:
+        pyext = env['BUILDERS']['PythonExtension']
+    except KeyError:
+        import SCons.Action
+        import SCons.Defaults
+        action = SCons.Action.Action("$PYEXTLINKCOM", "$PYEXTLINKCOMSTR")
+        action_list = [ SCons.Defaults.SharedCheck,
+                        action]
+        pyext = SCons.Builder.Builder(action = action_list,
+                                      emitter = "$SHLIBEMITTER",
+                                      prefix = '$PYEXTPREFIX',
+                                      suffix = '$PYEXTSUFFIX',
+                                      target_scanner = ProgramScanner,
+                                      src_suffix = '$PYEXTOBJSUFFIX',
+                                      src_builder = 'PythonObject')
+        env['BUILDERS']['PythonExtension'] = pyext
+
+    return pyext
+
+def pyext_coms(platform):
+    """Return PYEXTCCCOM, PYEXTCXXCOM and PYEXTLINKCOM for the given
+    platform."""
+    if platform == 'win32':
+        pyext_cccom = "$PYEXTCC /Fo$TARGET /c $PYEXTCCSHARED "\
+                      "$PYEXTCFLAGS $PYEXTCCFLAGS $_CCCOMCOM "\
+                      "$_PYEXTCPPINCFLAGS $SOURCES"
+        pyext_cxxcom = "$PYEXTCXX /Fo$TARGET /c $PYEXTCSHARED "\
+                       "$PYEXTCXXFLAGS $PYEXTCCFLAGS $_CCCOMCOM "\
+                       "$_PYEXTCPPINCFLAGS $SOURCES"
+        pyext_linkcom = '${TEMPFILE("$PYEXTLINK $PYEXTLINKFLAGS '\
+                        '/OUT:$TARGET.windows $( $_LIBDIRFLAGS $) '\
+                        '$_LIBFLAGS $_PYEXTRUNTIME $SOURCES.windows")}'
+    else:
+        pyext_cccom = "$PYEXTCC -o $TARGET -c $PYEXTCCSHARED "\
+                      "$PYEXTCFLAGS $PYEXTCCFLAGS $_CCCOMCOM "\
+                      "$_PYEXTCPPINCFLAGS $SOURCES"
+        pyext_cxxcom = "$PYEXTCXX -o $TARGET -c $PYEXTCSHARED "\
+                       "$PYEXTCXXFLAGS $PYEXTCCFLAGS $_CCCOMCOM "\
+                       "$_PYEXTCPPINCFLAGS $SOURCES"
+        pyext_linkcom = "$PYEXTLINK -o $TARGET $PYEXTLINKFLAGS "\
+                        "$SOURCES $_LIBDIRFLAGS $_LIBFLAGS $_PYEXTRUNTIME"
+
+    if platform == 'darwin':
+        pyext_linkcom += ' $_FRAMEWORKPATH $_FRAMEWORKS $FRAMEWORKSFLAGS'
+
+    return pyext_cccom, pyext_cxxcom, pyext_linkcom
+
+def set_basic_vars(env):
+    # Set construction variables which are independant on whether we are using
+    # distutils or not.
+    env['PYEXTCPPPATH'] = SCons.Util.CLVar('$PYEXTINCPATH')
+
+    env['_PYEXTCPPINCFLAGS'] = '$( ${_concat(INCPREFIX, PYEXTCPPPATH, '\
+                               'INCSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)'
+    env['PYEXTOBJSUFFIX'] = '$SHOBJSUFFIX'
+    env['PYEXTOBJPREFIX'] = '$SHOBJPREFIX'
+
+    env['PYEXTRUNTIME']   = SCons.Util.CLVar("")
+    # XXX: this should be handled with different flags
+    env['_PYEXTRUNTIME']  = '$( ${_concat(LIBLINKPREFIX, PYEXTRUNTIME, '\
+                          'LIBLINKSUFFIX, __env__)} $)'
+    # XXX: This won't work in all cases (using mingw, for example). To make
+    # this work, we need to know whether PYEXTCC accepts /c and /Fo or -c -o.
+    # This is difficult with the current way tools work in scons.
+    pycc, pycxx, pylink = pyext_coms(sys.platform)
+                            
+    env['PYEXTLINKFLAGSEND'] = SCons.Util.CLVar('$LINKFLAGSEND')
+
+    env['PYEXTCCCOM'] = pycc
+    env['PYEXTCXXCOM'] = pycxx
+    env['PYEXTLINKCOM'] = pylink
+
+def _set_configuration_nodistutils(env):
+    # Set env variables to sensible values when not using distutils
+    def_cfg = {'PYEXTCC' : '$SHCC',
+               'PYEXTCFLAGS' : '$SHCFLAGS',
+               'PYEXTCCFLAGS' : '$SHCCFLAGS',
+               'PYEXTCXX' : '$SHCXX',
+               'PYEXTCXXFLAGS' : '$SHCXXFLAGS',
+               'PYEXTLINK' : '$LDMODULE',
+               'PYEXTSUFFIX' : '$LDMODULESUFFIX',
+               'PYEXTPREFIX' : ''}
+
+    if sys.platform == 'darwin':
+        def_cfg['PYEXTSUFFIX'] = '.so'
+
+    for k, v in def_cfg.items():
+        ifnotset(env, k, v)
+
+    ifnotset(env, 'PYEXT_ALLOW_UNDEFINED', 
+             SCons.Util.CLVar('$ALLOW_UNDEFINED'))
+    ifnotset(env, 'PYEXTLINKFLAGS', SCons.Util.CLVar('$LDMODULEFLAGS'))
+
+    env.AppendUnique(PYEXTLINKFLAGS = env['PYEXT_ALLOW_UNDEFINED'])
+
+def ifnotset(env, name, value):
+    if not env.has_key(name):
+        env[name] = value
+
+def set_configuration(env, use_distutils):
+    """Set construction variables which are platform dependants.
+
+    If use_distutils == True, use distutils configuration. Otherwise, use
+    'sensible' default.
+
+    Any variable already defined is untouched."""
+
+    # We define commands as strings so that we can either execute them using
+    # eval (same python for scons and distutils) or by executing them through
+    # the shell.
+    dist_cfg = {'PYEXTCC': "sysconfig.get_config_var('CC')", 
+                'PYEXTCFLAGS': "sysconfig.get_config_var('CFLAGS')", 
+                'PYEXTCCSHARED': "sysconfig.get_config_var('CCSHARED')", 
+                'PYEXTLINKFLAGS': "sysconfig.get_config_var('LDFLAGS')", 
+                'PYEXTLINK': "sysconfig.get_config_var('LDSHARED')", 
+                'PYEXTINCPATH': "sysconfig.get_python_inc()", 
+                'PYEXTSUFFIX': "sysconfig.get_config_var('SO')"}
+
+    from distutils import sysconfig
+
+    # We set the python path even when not using distutils, because we rarely
+    # want to change this, even if not using distutils
+    ifnotset(env, 'PYEXTINCPATH', sysconfig.get_python_inc())
+
+    if use_distutils:
+        for k, v in dist_cfg.items():
+            ifnotset(env, k, eval(v))
+    else:
+        _set_configuration_nodistutils(env)
+
+def generate(env):
+    """Add Builders and construction variables for python extensions to an
+    Environment."""
+
+    if not env.has_key('PYEXT_USE_DISTUTILS'):
+        env['PYEXT_USE_DISTUTILS'] = False
+
+    # This sets all constructions variables used for pyext builders. 
+    set_basic_vars(env)
+
+    set_configuration(env, env['PYEXT_USE_DISTUTILS'])
+
+    # Create the PythonObject builder
+    pyobj = createPythonObjectBuilder(env)
+    action = SCons.Action.Action("$PYEXTCCCOM", "$PYEXTCCCOMSTR")
+    pyobj.add_emitter('.c', SCons.Defaults.SharedObjectEmitter)
+    pyobj.add_action('.c', action)
+
+    action = SCons.Action.Action("$PYEXTCXXCOM", "$PYEXTCXXCOMSTR")
+    pyobj.add_emitter('$CXXFILESUFFIX', SCons.Defaults.SharedObjectEmitter)
+    pyobj.add_action('$CXXFILESUFFIX', action)
+
+    # Create the PythonExtension builder
+    createPythonExtensionBuilder(env)
+
+def exists(env):
+    try:
+        # This is not quite right: if someone defines all variables by himself,
+        # it would work without distutils
+        from distutils import sysconfig
+        return True
+    except ImportError:
+        return False

tests/run/locals.pyx

 __doc__ = u"""
 >>> sorted( get_locals(1,2,3, k=5) .items())
 [('args', (2, 3)), ('kwds', {'k': 5}), ('x', 1), ('y', 'hi'), ('z', 5)]
-"""
 
-import sys
-IS_PY3 = sys.version_info[0] >= 3
+>>> in_locals('z')
+True
+>>> in_locals('args')
+True
+>>> in_locals('X')
+False
+"""
 
 def get_locals(x, *args, **kwds):
     cdef int z = 5
-    if IS_PY3:
-        y = u"hi"
-    else:
     y = "hi"
     return locals()
 
+def in_locals(x, *args, **kwds):
+    cdef int z = 5
+    y = "hi"
+    return x in locals()
+
 def sorted(it):
     l = list(it)
     l.sort()

tests/run/locals_expressions_T430.pyx

+__doc__ = u"""
+>>> sorted( get_locals(1,2,3, k=5) .items())
+[('args', (2, 3)), ('kwds', {'k': 5}), ('x', 1), ('y', 'hi'), ('z', 5)]
+
+>>> sorted(get_locals_items(1,2,3, k=5))
+[('args', (2, 3)), ('kwds', {'k': 5}), ('x', 1), ('y', 'hi'), ('z', 5)]
+
+>>> sorted(get_locals_items_listcomp(1,2,3, k=5))
+[('args', (2, 3)), ('kwds', {'k': 5}), ('x', 1), ('y', 'hi'), ('z', 5)]
+"""
+
+def get_locals(x, *args, **kwds):
+    cdef int z = 5
+    y = "hi"
+    return locals()
+
+def get_locals_items(x, *args, **kwds):
+    cdef int z = 5
+    y = "hi"
+    return locals().items()
+
+def get_locals_items_listcomp(x, *args, **kwds):
+    cdef int z = 5
+    y = "hi"
+    return [ item for item in locals().items() ]
+
+def sorted(it):
+    l = list(it)
+    l.sort()
+    return l

tests/run/locals_rebind_T429.pyx

+__doc__ = u"""
+>>> sorted( get_locals(1,2,3, k=5) .items())
+[('args', (2, 3)), ('kwds', {'k': 5}), ('x', 1), ('y', 'hi'), ('z', 5)]
+
+>>> get_locals_rebound(1,2,3)
+'REBOUND'
+"""
+
+def get_locals(x, *args, **kwds):
+    cdef int z = 5
+    y = "hi"
+    return locals()
+
+def get_locals_rebound(x, *args, **kwds):
+    cdef int z = 5
+    locals = _locals
+    y = "hi"
+    return locals()
+
+def _locals(): return "REBOUND"
+
+def sorted(it):
+    l = list(it)
+    l.sort()
+    return l

tests/run/parallel_swap_assign_T425.pyx

-__doc__ = u"""
->>> swap(1,2)
-(2, 1)
-"""
 
+cimport cython
+
+@cython.test_assert_path_exists(
+    "//ParallelAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode/NameNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode[@use_managed_ref=False]/NameNode",
+    )
+@cython.test_fail_if_path_exists(
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode[@use_managed_ref=True]",
+    )
 def swap(a,b):
+    """
+    >>> swap(1,2)
+    (2, 1)
+    """
     a,b = b,a
     return a,b
+
+
+@cython.test_assert_path_exists(
+    "//ParallelAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode/NameNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode[@use_managed_ref=False]/NameNode",
+    )
+@cython.test_fail_if_path_exists(
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode[@use_managed_ref=True]",
+    )
+def swap5(a,b,c,d,e):
+    """
+    >>> swap5(1,2,3,4,5)
+    (5, 4, 3, 2, 1)
+    """
+    a,b,c,d,e = e,d,c,b,a
+    return a,b,c,d,e
+
+
+@cython.test_assert_path_exists(
+    "//ParallelAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode/NameNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode[@use_managed_ref=False]/NameNode",
+    )
+@cython.test_fail_if_path_exists(
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode[@use_managed_ref=True]",
+    )
+cdef bint c_swap_cmp5(a, b, c, d, e):
+    a,b,c,d,e = e,d,c,b,a
+    return a > b > c > d > e
+
+def swap_cmp5(a,b,c,d,e):
+    """
+    >>> swap_cmp5(1,2,3,4,5)
+    True
+    """
+    return c_swap_cmp5(a,b,c,d,e)
+
+
+@cython.test_assert_path_exists(
+    "//ParallelAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode/NameNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode[@use_managed_ref=True]/NameNode",
+    )
+@cython.test_fail_if_path_exists(
+    "//ParallelAssignmentNode/SingleAssignmentNode//CoerceToTempNode[@use_managed_ref=False]",
+    )
+def swap_py(a,b):
+    a,a = b,a
+    return a,b
+
+
+@cython.test_assert_path_exists(
+#    "//ParallelAssignmentNode",
+#    "//ParallelAssignmentNode/SingleAssignmentNode",
+#    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode",
+#    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode[@use_managed_ref=False]",
+    )
+@cython.test_fail_if_path_exists(
+#    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode[@use_managed_ref=True]",
+    )
+def swap_list_items(list a, int i, int j):
+    """
+    >>> l = [1,2,3,4]
+    >>> swap_list_items(l, 1, 2)
+    >>> l
+    [1, 3, 2, 4]
+    >>> swap_list_items(l, 3, 0)
+    >>> l
+    [4, 3, 2, 1]
+    >>> swap_list_items(l, 0, 5)
+    Traceback (most recent call last):
+    IndexError: list index out of range
+    >>> l
+    [4, 3, 2, 1]
+    """
+    a[i], a[j] = a[j], a[i]
+
+
+@cython.test_assert_path_exists(
+    "//ParallelAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode[@use_managed_ref=True]",
+    )
+@cython.test_fail_if_path_exists(
+    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode[@use_managed_ref=False]",
+    )
+def swap_list_items_py1(list a, int i, int j):
+    a[i], a[j] = a[j+1], a[i]
+
+
+@cython.test_assert_path_exists(
+    "//ParallelAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode",
+    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode[@use_managed_ref=True]",
+    )
+@cython.test_fail_if_path_exists(
+    "//ParallelAssignmentNode/SingleAssignmentNode//IndexNode[@use_managed_ref=False]",
+    )
+def swap_list_items_py2(list a, int i, int j):
+    a[i], a[j] = a[i], a[i]