Re: [ff3d-users] Newbie question

[Luigi Bardelli]

Hi Stephane,
  thank you for the quick reply! I'm not understanding why the various
expressions do not work when A is a PDE variable like for example

solve(v1,v2) in MESH{
  pde(v1)
    v1*dx(dx(v2))=0
  pde(v2)
    .....
}
it says:
   syntax error, unexpected '*', expecting '=' or '-' or '+': "*"
unexpected

Why? Thank you
   Luigi



On Wed, 21 Jul 2004, Stephane Del Pino wrote:
> Luigi Bardelli wrote:
> >
> > Hi Stephane,
> >    thank you, now it works! I have another question (maybe related):
> > writing something  like:
> >
> > double A=0.123456789; // constant for
> > solve(var) in MESH
> > {
> >   pde(var)
> >     //    dx(dx(var))=0;    //  ok
> >     //    A*dx(dx(var))=0;  // not ok
> >     //    -dx(dx(var))=0;   //  ok
> >     //    dx(dx(var))*A=0;  // not ok
> >     //    dx(dx(A*var))=0;  // not ok
> >     //    -dx(dx(A*var))=0; // not ok
> >     //    -dx(A*dx(var))=0; //  ok !
> >     //    dx(A*dx(var))=0;  //  ok !
> > }
> >
> > sometimes gives errors like:
> > line 103:syntax error, unexpected "unkown variable": "var" unexpected
> >
> > If A is a pde unknown the error changes in
> > line 103:syntax error, unexpected '*', expecting '=' or '-' or '+': "*"
> > unexpected
> >
> > Is it normal?
> Yes !
> ff3d is not very clever and does not know that if A is constant
>       A*dx(dx(u)) = dx(A*dx(u))
> In fact, if A is not constant, you need to write it dx(A*dx(u)) to use
> the Green formula in order to establish the variationnal formula.
> I think this answers the question...
>
> > Another (minor) remark: in docs/Makefile.am the line
> >         dvips `basename $< .tex`.dvi
> > should be changed in something like
> >         dvips `basename $< .tex`.dvi -o  `basename $< .tex`.ps
> > otherwise the manual will be printed on the default printer every time you
> > compile the lib (I have already two copies...)
> Ooops.
> I thought this was fixed. Maybe it stayed in my developing version. I
> will look at it this evening...
>
> Stephane.
>
>
> _______________________________________________
> ff3d-users mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/ff3d-users
>