This is a followup to the thread at
http://www.math.utexas.edu/pipermail/maxima/2011/024575.html from last
year, some of which I copy below. I'm just wondering if this was ever
reported as a bug on the bug tracker? The only related ticket I can
find is http://sourceforge.net/tracker/index.php?func=detail&aid=1676034&group_id=4933&atid=104933
but I didn't want to open one until I was sure. It's certainly still
there:
Maxima 5.27.0 http://maxima.sourceforge.net
using Lisp SBCL 1.0.24
(%i7) display2d:false;
(%o7) false
(%i8) desolve([diff(f(x),x)=f(x^2)],[f(x)]);
(%o8) f(x) = 'ilt(('laplace(f(x^2),x,?g1021)+f(0))/?g1021,?g1021,x)
Thanks!
+++
This is a bug: Maxima output should never include bare Lisp symbols (unless
of course the user entered them), and should never include Lisp gensyms
(which cannot be input by the user). Apparently desolve uses Lisp gensyms
in the expectation that ilt/laplace will eliminate them
Of course, if Sage allowed initial "?" in symbol names, this particular
problem would go away. (Though it does seem weird that Sage is using the
stringout form of expressions rather than the s-expressions to communicate
with Maxima.)
-s
PS It would help if the actual call to Maxima were included in reports like
this, rather than the Sage form. In particular, I don't quite get the
x1=function('x1',t) construction. I reproduced the problem with
de1: diff(x1(t),t)=-3*(x2(t)^2-1);
de2: diff(x2(t),t)=1;
desolve([de1,de2],[x1(t),x2(t)]);
A simpler example:
desolve([diff(f(x),x)=f(x^2)],[f(x)]);
On Mon, Mar 14, 2011 at 17:07, Robert Dodier <robert.dodier at gmail.com>wrote:
> Short answer is that ?g1234 etc are so-called gensyms,
> that is, generated Lisp symbols.
>
> Looks like ?g1811 is a dummy variable in the Laplace transform.
> On the face of it, it looks correct, but desolve could
> pick a less confusing name.
>
> best
>