Updates:
Labels: EasyToFix
Comment #5 on issue 3743 by smi...@gmail.com: dummy_eq fails with Sum
http://code.google.com/p/sympy/issues/detail?id=3743
I think this will work
def dummy_eq(self, other):
"""
Compare two expressions and handle dummy symbols.
Examples
========
>>> from sympy import Dummy
>>> from sympy.abc import x, y
>>> u = Dummy('u')
>>> (u**2 + 1).dummy_eq(x**2 + 1)
True
>>> (u**2 + 1) == (x**2 + 1)
False
>>> (u**2 + y).dummy_eq(x**2 + y, x)
True
>>> (u**2 + y).dummy_eq(x**2 + y, y)
False
"""
def not_free(eq):
free = eq.free_symbols
return [a for a in preorder_traversal(eq)
if isinstance(a, C.Symbol) and a not in free]
s = not_free(self)
o = not_free(other)
if not s:
return self == other
if len(s) != len(o):
return False
return self.xreplace(dict(zip(s, o))) == other
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