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