>> We won't be able to support such output with our new output API >> assert solve(x - exp(x), x, implicit=True) == [exp(x)]
> How is this implemented? I read the code and it appears. Things like exp(x) are replaced by dummy symbols and then solve is allowed to run on it. After the solution is obtained the dummy symbols are replaced back with their original values. On 17 March 2014 05:53, Aaron Meurer <[email protected]> wrote: > Looking through my notes > (https://github.com/sympy/sympy/wiki/assumptions_handlers, pardon the > formatting; it looks better in emacs), I see that most of the wrong > results I saw were not in the "core" facts, like positive or real > (other than the ones you probably already knew about with infinities > https://github.com/sympy/sympy/issues/5976). It looks like most of the > blatant wrong results that I found were in ntheory (and yes, I am > guilty of not ever opening issues for these things) > > In [2]: ask(Q.prime(x*y), Q.integer(x)&Q.integer(y)) > Out[2]: False > > In [3]: ask(Q.prime(x**y), Q.integer(x)&Q.integer(y)) > Out[3]: False > > In [6]: ask(Q.integer(abs(x)), ~Q.integer(x)) > Out[6]: False > > I leave it as an exercise to the reader why each of the above is incorrect. > > But more to the point, as I noted in at the bottom of that wiki page, > the new assumptions handlers code is very fragile. If you accidentally > use the wrong kind of Python logic instead of fuzzy logic, you can > return False instead of None. In the best case, you just end up not > implementing as much as you thought you were, but in the worst case, > you get a wrong result. > > There are subtle issues that can come up (similar to the > https://github.com/sympy/sympy/issues/5976 one) with the new > assumptions not being consistant in how it defines assumptions. It > doesn't help that it quite often calls out to some external routine to > calculate something, which may or may not use the same definition of > the assumption that it does. It also uses evalf on most assumptions > relating to numbers, which can have its own issues. > > Aaron Meurer > > On Sun, Mar 16, 2014 at 5:32 PM, Matthew Rocklin <[email protected]> > wrote: > > Recall that sets mostly lives in the core. In particular I think that > > Interval and maybe Union have been used in the core for some time and > > FiniteSet has made itself useful in the last couple years. > > > > > > On Sun, Mar 16, 2014 at 3:31 PM, Matthew Rocklin <[email protected]> > wrote: > >> > >> > By the way, I didn't know that the sets use exclusively the new > >> > assumptions (assuming that is indeed what you are saying here). > >> > >> That is not what I'm saying. S.Integers and S.Naturals use new > >> assumptions. Most of the logic behind core sets doesn't explicitly > think > >> about assumptions at all. So, perhaps worse, sets implicitly uses some > >> combination of the two. > >> > >> > >> On Sun, Mar 16, 2014 at 2:16 PM, Harsh Gupta <[email protected]> > >> wrote: > >>> > >>> Sorry I accidently pushed Send, ( I was unconsciously entering some vim > >>> commands). Ignore the "For" after the example. > >>> > >>> -- > >>> Harsh > >>> > >>> -- > >>> 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/CADN8iupYZiJoBNQxCiAtg0Y-bXF1fNs2PbQtdh9qvYd765L7Sw%40mail.gmail.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/CAJ8oX-FnZjs4vfBFh%3D2WtMvRdaEM-ndNW%2BqL-rNk5EYQhQ3hVQ%40mail.gmail.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%3D6L5k4Lvep%3DjVvLPbU6JW%3DMrwsrLsV%2Bq3hAFBQr7XDFdoA%40mail.gmail.com > . > For more options, visit https://groups.google.com/d/optout. > -- Harsh -- 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/CADN8iuq2u3mypUpyBwqYbu1ZhVH%2BNv81z1OKX1yiXAS8U67ptA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
