I would make a pull request. Then Travis CI will run the tests and if anything fails you can see if it has unpredicted implications on some other part of the codebase. And if not, it is probably fine.
Aaron Meurer On Wed, Apr 1, 2015 at 11:23 AM, Duane Nykamp <[email protected]> wrote: > I found a solution that works for me, but since I don't understand how the > sorting work or all the places where it fits in, I'm unsure of the merits of > the solution. > > I just made a couple changes to .as_terms from expr.py, as shown in the diff > below. The idea is that > 1) since a given base can show up multiple times in a term, we have to add > up the exponents from all instances, and > 2) since the exponent alone doesn't distinguish x*x from x**2, we also keep > track of how many times the base appeared. > > I stored this information in a tuple so that x*x is represented by (2,2) and > x**2 is represented by (2,1). > > With the change, an unevaluated polynomial sorts its terms in a consistent > way. > > In [4]: Add(x, x**3, x, Mul(x,x,x,evaluate=False), x, Mul(x**2,x, > evaluate=False), x**3, evaluate=False) > Out[4]: > 2 3 3 > x⋅x⋅x + x⋅x + x + x + x + x + x > > If this seems reasonable, I could make a pull request. > > Duane > > > diff --git a/sympy/core/expr.py b/sympy/core/expr.py > index 0de02ff..c9093f0 100644 > --- a/sympy/core/expr.py > +++ b/sympy/core/expr.py > @@ -928,7 +928,8 @@ def as_terms(self): > if factor.is_commutative: > base, exp = decompose_power(factor) > > - cpart[base] = exp > + prev = cpart.get(base,(0,0)) > + cpart[base] = (prev[0]+exp, prev[1]+1) > gens.add(base) > else: > ncpart.append(factor) > > > > On Tuesday, March 31, 2015 at 5:04:37 PM UTC-5, Duane Nykamp wrote: >> >> The sort key seems insufficient for sorting unevaluated expressions. >> >> In [37]: Add(x, Mul(x,x,x,evaluate=False), x, evaluate=False) >> Out[37]: x + x⋅x⋅x + x >> >> With a slight change, it works as expected: >> >> In [38]: Add(x, Mul(x,y,x,evaluate=False), x, evaluate=False) >> Out[38]: x⋅x⋅y + x + x >> >> It seems that the sort key is the same for all three terms in the case >> that doesn't work. >> In [43]: poly=Add(x, Mul(x,x,x,evaluate=False), x, x, evaluate=False) >> >> In [49]: terms, gens = poly.as_terms() >> >> In [56]: key, reverse = poly._parse_order(None) >> >> In [57]: key(terms[0]) >> Out[57]: ((-1,), (), ((False, 0.0), (1.0, 0.0))) >> >> In [58]: key(terms[1]) >> Out[58]: ((-1,), (), ((False, 0.0), (1.0, 0.0))) >> >> In [59]: key(terms[2]) >> Out[59]: ((-1,), (), ((False, 0.0), (1.0, 0.0))) >> >> Since the key function completely ignores the first component of each >> term, I'm guessing that the remaining components of the term data structure >> all supposed to encode all the useful information. Except for the first >> component, each term is identical, which I believe to be the source of the >> problem. >> >> In [68]: terms[0] >> Out[68]: (x, ((1.0, 0.0), (1, 0), ())) >> >> In [69]: terms[1] >> Out[69]: (x⋅x⋅x, ((1.0, 0.0), (1, 0), ())) >> >> In [70]: terms[2] >> Out[70]: (x, ((1.0, 0.0), (1, 0), ())) >> >> I can't say I understand all the ways in which terms are used, so I don't >> know what would be an appropriate fix. But, clearly, it's broken for the >> terms one gets with unevaluated functions. >> >> Any idea on how to fix it? >> >> Duane > > -- > 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 http://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/8b727451-a1b3-4c5e-820d-7f06b93db6cc%40googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. -- 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 http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6K%2BNj-bXJZ1J_Bud7DE%2BHFV4W%3DTFqsf8NzmbjNHOaPo%3Dw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
