##############################################################################
#
# Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.0 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE
#
##############################################################################
__version__='$Revision: 1.6 $'[11:-2]
from SelectCompiler import ast
ListType = type([])
TupleType = type(())
SequenceTypes = (ListType, TupleType)
class MutatingWalker:
def __init__(self, visitor):
self.visitor = visitor
self._cache = {}
def defaultVisitNode(self, node, walker=None, exclude=None):
for name, child in node.__dict__.items():
if exclude is not None and name in exclude:
continue
v = self.dispatchObject(child)
if v is not child:
# Replace the node.
node.__dict__[name] = v
return node
def visitSequence(self, seq):
res = seq
for idx in range(len(seq)):
child = seq[idx]
v = self.dispatchObject(child)
if v is not child:
# Change the sequence.
if type(res) is ListType:
res[idx : idx + 1] = [v]
else:
res = res[:idx] + (v,) + res[idx + 1:]
return res
def dispatchObject(self, ob):
'''
Expected to return either ob or something that will take
its place.
'''
if isinstance(ob, ast.Node):
return self.dispatchNode(ob)
elif type(ob) in SequenceTypes:
return self.visitSequence(ob)
else:
return ob
def dispatchNode(self, node):
klass = node.__class__
meth = self._cache.get(klass, None)
if meth is None:
className = klass.__name__
meth = getattr(self.visitor, 'visit' + className,
self.defaultVisitNode)
self._cache[klass] = meth
return meth(node, self)
def walk(tree, visitor):
return MutatingWalker(visitor).dispatchNode(tree)
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