I created an AddUnsort class that doesn't change the order of its
argument. Now, I discovered I get an infinite recursion when I evalf.
But, I'm having trouble figuring out how to prevent this infinite recursion.
The still get the infinite recursion even with this stripped down class
that does very little to Add. The only change is that it doesn't evaluate
the arguments (it acts as long evaluate=False) and it doesn't order the
arguments.
from sympy import Add
from sympy.core.cache import cacheit
from sympy.core.sympify import _sympify
class AddUnsortPart(Add):
@cacheit
def __new__(cls, *args, **options):
# __new__ from AssocOp, with differences
# - we don't throw out the identity
# - we never evaluate
args = list(map(_sympify, args))
if len(args) == 0:
return cls.identity
if len(args) == 1:
return args[0]
return cls._from_args(args)
But, executing, for example,
AddUnsortPart(2,5).evalf()
gets an infinite loop between the _eval_evalf() function of AssocOp and
._evalf() of EvalfMixin. I'm obviously missing something here, as I don't
see why one usually doesn't get this infinite loop, so what I should do to
prevent this problem.
Any pointers would be helpful. The above stripped down class hardly
modifies Add at all, so it's puzzling why this change creates the problem.
(Of course, in the real class, I'm making a lot more changes to make it
useful AddUnsort class.)
Thanks,
Duane
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