I did the following bottom_up traversal and got an unexpected result:
>>> e
y*(x + 3) - y
>>> bottom_up(condition(lambda x:x.is_Add, lambda x:S.One))(e)
1
I confirmed with the debugger that Add(-y, y) is created but apparently in
an unevaluated manner. If it were evaluated, that should have collapsed to
0 and then there would be no Add to be identified as 1. If I try to slip a
recalculation of the x I get an error:
>>> cond = lambda x:Add(*Add.make_args(x)).is_Add
>>> bottom_up(condition(cond, lambda x:S.One))(e)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "sympy\rules\traverse.py", line 19, in bottom_up_rl
return rule(new(type(expr), *map(bottom_up_rl, expr.args)))
File "sympy\rules\strat_pure.py", line 27, in conditioned_rl
if cond(expr):
File "<stdin>", line 1, in <lambda>
File "sympy\core\cache.py", line 92, in wrapper
func_cache_it_cache[k] = r = func(*args, **kw_args)
File "sympy\core\operations.py", line 38, in __new__
c_part, nc_part, order_symbols = cls.flatten(args)
File "sympy\core\add.py", line 179, in flatten
noncommutative = noncommutative or not s.is_commutative
AttributeError: is_commutative
/c
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