On Jan 21, 3:05 am, David Joyner <wdjoy...@gmail.com> wrote:
> (However, for other problems, this trick will not work so well.)
> I know about the problem with desolve and don't know how
> to "fix" it (though, it is actually documented that way, as you will see if
> you type desolve?). Sorry.
I guess you know all that as an author, but, just in case, a few
thoughts about this issue.
When one looks at what Sage sends to Maxima when "desolve(diff(y,x,
2)+y(x)==0,y,[0,3,2])" is called, it turns out that Maxima receives
something like
my_ode: diff('y(x),x,2) + 'y(x) = 0;
my_sol: ode2(my_ode, 'y(x), x);
ic2(my_sol, x=0, 'y(x)=2, diff('y(x),x)=3);
and then Maxima returns "y(x) = 3 sin(x) + y(0) cos(x)", whereas the
documentation of Maxima's ode2 seems to expect that one should type:
my_ode: 'diff(y,x,2) + y = 0;
my_sol: ode2(my_ode, y, x);
ic2(my_sol, x=0, y=2, 'diff(y,x)=3);
in which case Maxima returns "y = 3 sin(x) + 2 cos(x)" (the expected
answer).
Therefore, one could think of:
(1) Patching Maxima so that it works also with what Sage sends to it.
Since this boils down to change [xa,ya] for [ya,xa] in the file share/
diffequations/ode2.mac of Maxima, it might be easy and I made a
(possibly clumsy) proposal on the Maxima mailing list.
(2) Patching only the version of Maxima that Sage uses.
(3) Patching Sage so that it checks that there is no y(0) left in the
solution and, if any, eliminates it by calling solve and substituting.
(4) Modifying Sage to that it sends to Maxima's ode2 and ic2 functions
what they actually expect (i.e. an O.D.E. and I.C. with y, not 'y(x)).
By the way, it is easy to modify $SAGE_ROOT/local/lib/python/site-
packages/sage/interfaces/maxima.py to actually see the communication
between Sage and Maxima, but there is maybe a direct and
straightforward way to do that that I missed (something like
"echo_interfaces=true" or "maxima_interface_echo=true")?
HTH,
Christophe Deroulers
University Paris Diderot-Paris 7, Physics Department
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