Hello everyone, It is my first post and I hope it is the right place to send my question. First I would like to thank all the developers who created this great library. We use it in my company but we encountered a very strange behavior. I wanted to do a PR to correct it but the tests show that this may be voluntary behavior.
The problem : even with "evaluate=False" argument, Mul and Add remove identity elements from its arguments. We can see this behavior in tests : https://github.com/sympy/sympy/blob/master/sympy/core/tests/test_arit.py#L1366 def test_suppressed_evaluation(): a = Add(0, 3, 2, evaluate=False) b = Mul(1, 3, 2, evaluate=False) c = Pow(3, 2, evaluate=False) assert a != 6 assert a.func is Add assert a.args == (3, 2) assert b != 6 assert b.func is Mul assert b.args == (3, 2) assert c != 9 assert c.func is Pow assert c.args == (3, 2) Removing arguments is already a kind of evaluation. For me, we should have : def test_suppressed_evaluation(): a = Add(0, 3, 2, evaluate=False) b = Mul(1, 3, 2, evaluate=False) # ... assert a.args == (0, 3, 2) # ... assert b.args == (1, 3, 2) # ... and do not remove any arguments. I can do a PR to change this behavior (and update tests), It seems to me that this can be corrected by moving the lines that remove identities elements right after the "evaluate" processing : move the line https://github.com/sympy/sympy/blob/master/sympy/core/operations.py#L31 after the if on line 33. I prefer to ask the question here before because the presence of the tests can make believe that this behavior is voluntary. Christophe Gabard -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/2b59c125-f424-459b-b5a1-f220e5ef7db2%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
