On Thu, Mar 27, 2008 at 11:29 PM, Nils Bruin <[EMAIL PROTECTED]> wrote: > > I tried the first example below in sage. It failed , complaining that > maxima wanted to know whether x was positive, negative or 0. Hence, I > tried maxima via "sage -maxima". To my surprise, maxima computed the > limit without asking for extra information. Is the maxima that gets > called from sage put in a more inquisitive mode? > > I figure this might be a symptom of a sub-optimal interaction between > sage and maxima and hence might have some interest to developers.
This is almost certainly related to us putting Maxima in "complex numbers" mode by default, since Maxima's non-complex mode is very stupid in numerous ways, as Paul Zimmerman has pointed out. > > > /////////////////////////////////////////////////////////////////////////////////// > %sage > var('p x') > limit((p+1)/pi*(1-x^2/4)/((sqrt(p)+sqrt(1/p))^2-x^2),p=oo) > > //complains that maxima wants extra information > > > //////////////////////////////////////////////////////////////////////////////////// > %maxima > f(p,x):=(p+1)/pi*(1-x^2/4)/((sqrt(p)+sqrt(1/p))^2-x^2); > limit(f(p,x),p, infinity); > > //works The issue is that you're passing in "infinity" which *not* what Sage converts oo to: sage: maxima(oo) inf sage: maxima('infinity') infinity Maxima has the "brilliant" design that inf = real infinity and infinity = complex infinity: (%i8) describe(infinity); -- Constant: infinity `infinity' represents complex infinity. (%o8) true (%i9) describe(inf); -- Constant: inf `inf' represents real positive infinity. I guess Maxima must not have a referee system for their code... Anyway, I'm not sure what to do about this. I don't even know what "complex infinity" means... But hopefully this sheds some light. By the way, if you ever design a computer algebra system, please don't make inf and infinity be two different kinds of infinity. Gees that's almost as confusing as making Matrix and matrix drastically different[*]. -- William [*] Maple does this. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---