On Friday, March 13, 2015 at 11:32:11 AM UTC-7, M M wrote: > > I tried on a different machine with Sage Version 6.5, Release Date: > 2015-02-17 and I get the same behaviour described in the original post. > Where parsing a string and evaluating returns different results than using > the resulted sage expression. > > Ah, right. Yes, evaluating a string representation of an object does necessarily result in the same object. We have already established that the expression in question is ill-conditioned for numerical purposes, so you probably end up with a subtly different internal representation of the object, which has huge numerical consequences. Indeed:
sage: A = integral(x/(x^3-x+1), x, 1, 2) sage: B = eval(preparse(str(A))) sage: (A-B).n() 0.894231297231034 sage: (A-B).simplify() 0 This is entirely consistent with float operations not being commutative/associative/etc. It's unfortunate, but if this is a bug then floating point is a bug. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
