Re: [ff3d-users] Newbie question

[Stephane Del Pino]

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.