Hi,
On Wed, Aug 19, 2009 at 2:30 PM, William Stein<wst...@gmail.com> wrote: > > On Tue, Aug 18, 2009 at 11:00 PM, Ondrej Certik<ond...@certik.cz> wrote: >> >> well, I would interpret it differently: >> >> int f(x) d(x^2) = int f(x) 2 x dx >> = 2 integrate(x*f(x),x) > > That's exactly what I meant. I was just being very sloppy because I > was in a hurry. The point is that "int f(x) d(x^2) = int f(x) 2 x > dx" seems very reasonable. We could easily make Sage use this > interpretation even though Maxima doesn't. It woud be an additional > 2-3 lines of code in calculus.py. > > I am equally for either: > > (1) raising an error like Mathematica does > and > (2) Use the interpretation that Ondrej and I agree upon above. > > I favor (1) a little bit more than (2), because it's clear that there > is some confusion over this issue Hmm, could you please clarify a bit? When you say "raise an error" do you mean (A) (damn the user!!) ------- sage: integrate( sin(x), x^2) .... TypeError: blah.. blah... ------- or (B) (leave it symbolic) ------- sage: integrate(f(x), x^2) integrate( sin(x), x^2) ------- (A) will have some bad consequences like ----- sage: h = sin(x) + integrate( sin(x), x) sage: h.subs(x==2*x) sin(2*x) - cos(2*x) ----- will work but ----- sage: h = sin(x) + integrate( sin(x)/x, x) sage: h.subs(x==2*x) ... TypeError: ..... ----- It would be bad if we don't allow even constant scaling of variable in the integration. I guess, there are no ambiguity when it is an expression containing single variable and we should process it as you and Ondrej suggested. For other cases, we leave it symbolic as Robert (Dodier) suggested. Cheers, Golam --~--~---------~--~----~------------~-------~--~----~ To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
