> you might simplify infinity-infinityto 0, Well, this is the wrong thing here... but sage is smarter than that, I believe.
On Saturday, 11 March 2017 19:09:07 UTC+2, rjf wrote: > > > > On Wednesday, March 1, 2017 at 2:11:41 AM UTC-8, Peleg Michaeli wrote: >> >> Hi, >> >> I have two questions, one might be thought of as a bug report / feature >> request, please tell me what you think. Trying >> integrate(x, x, 0, infinity) >> raises ValueError: Integral is divergent. >> >> My first question: why it does not simply return infinity? >> > > Arguably, infinity as an answer is bogus, and it might be more > appropriate to signal a problem. > > Why? If you return such an answer and continue to compute with it > (without displaying it ever to the user) you might simplify > infinity-infinity > to 0, infinity/infinity to 1, etc. So you would never know that you > did bogus arithmetic, and just get a bogus answer. > > > >> (it does, by the way, if one chooses algorithm='sympy') >> >> Now, trying >> integrate(ceil(x), x, 0, infinity) >> returns something weird: >> limit(1/2*(2*x + 1)*ceil(x) - 1/2*ceil(x)^2, x, +Infinity, minus) >> and trying to evaluate it with `.n()` raises TypeError. >> >> My second question: why it does not return infinity / raises ValueError: >> Integral is divergent..? >> >> And now, two more observations, which are certainly bugs: >> >> Bug 1: running >> integrate(ceil(x), x, 0, infinity, algorithm='sympy') >> raises AttributeError: 'module' object has no attribute 'ceiling'. I am >> not sure, but I think that the problem is that in sympy there's no `ceil` >> but rather `ceiling`. >> >> Bug 2: running >> integrate(floor(x), x, 0, infinity, algorithm='sympy') >> returns >> integrate(floor(x), x, 0, +Infinity) >> and trying to evaluate it with `.n()` returns (!!) >> -679.7441466712775 >> >> Should I open 2 tickets for these last two bugs? >> >> >> Thanks, >> Peleg. >> >> >> >> >> >> -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
