52 lines
2.1 KiB
Python
52 lines
2.1 KiB
Python
# Copyright (c) 2015 Marc Brinkmann
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# Permission is hereby granted, free of charge, to any person obtaining a
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# copy of this software and associated documentation files (the "Software"),
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# to deal in the Software without restriction, including without limitation
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# the rights to use, copy, modify, merge, publish, distribute, sublicense,
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# and/or sell copies of the Software, and to permit persons to whom the
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# Software is furnished to do so, subject to the following conditions:
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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# DEALINGS IN THE SOFTWARE.
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class Visitor(object):
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"""Base class for visitors."""
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def visit(self, node):
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"""Visit a node.
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Calls ``visit_CLASSNAME`` on itself passing ``node``, where
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``CLASSNAME`` is the node's class. If the visitor does not implement an
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appropriate visitation method, will go up the
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`MRO <https://www.python.org/download/releases/2.3/mro/>`_ until a
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match is found.
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If the search exhausts all classes of node, raises a
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:class:`~exceptions.NotImplementedError`.
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:param node: The node to visit.
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:return: The return value of the called visitation function.
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"""
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if isinstance(node, type):
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mro = node.mro()
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else:
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mro = type(node).mro()
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for cls in mro:
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meth = getattr(self, 'visit_' + cls.__name__, None)
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if meth is None:
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continue
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return meth(node)
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raise NotImplementedError('No visitation method visit_{}'
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.format(node.__class__.__name__))
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