26 lines
799 B
Python
26 lines
799 B
Python
""" Branching Strategies to Traverse a Tree """
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from itertools import product
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from sympy.strategies.util import basic_fns
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from .core import chain, identity, do_one
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def top_down(brule, fns=basic_fns):
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""" Apply a rule down a tree running it on the top nodes first """
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return chain(do_one(brule, identity),
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lambda expr: sall(top_down(brule, fns), fns)(expr))
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def sall(brule, fns=basic_fns):
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""" Strategic all - apply rule to args """
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op, new, children, leaf = map(fns.get, ('op', 'new', 'children', 'leaf'))
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def all_rl(expr):
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if leaf(expr):
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yield expr
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else:
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myop = op(expr)
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argss = product(*map(brule, children(expr)))
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for args in argss:
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yield new(myop, *args)
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return all_rl
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