On Sun, Feb 1, 2009 at 5:34 PM, Christophe Deroulers
<[email protected]> wrote:
>
>
> 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).
>
Thanks, this is very interesting.
In this case, it seems that the subfunction
def to_eqns(lhs, exprs):
eqns = []
for lhs, expr in zip(lhs, exprs):
if isinstance(expr, SymbolicEquation):
eqns.append(expr)
else:
if lhs == dvar and len(exprs) == 2:
ivar_ic = exprs[0] # figure this out...
lhs = lhs._f(ivar_ic)
eqns.append(lhs == expr)
in desolver needs to be modified somehow. It sets the
syntax of the initial conditions passed to maxima.
> Therefore, one could think of:
>
...
>
> (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)).
>
I think this is the most natural way to go but I don't see how to do it.
> 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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