[Gambas-user] Gambas3 and Gnu scientific library

[wally]

Thanks a lot ! :)   
wally

On Wednesday, May 18, 2011 17:07:09 Benoît Minisini wrote:
> > Hello  Jussi,
> > 
> > in C the stuff works pretty nice, so i agree to your suggestion 2.
> > 
> > Do all math stuff directly in Gambas is an option i should check.
> > 
> > I think i mentioned that i use Gambas3 and want to make interpolations,
> > derivatives and integrals from an integrarray.
> > The array contains ADC outputs from a CCD linear array sensor measurment
> > 
> > wally
> > 
> > On Monday, May 16, 2011 17:46:51 Jussi Lahtinen wrote:
> > > Not very easy task...
> > > Here is interpolation example in C.
> > > http://www.gnu.org/software/gsl/manual/html_node/Interpolation-Example-
> > > pr og rams.html
> > > 
> > > As you can see, you need to call several functions to get what you
> > > want. Declaring those in Gambas is OK, except determining
> > > interpolation type!
> > > 
> > > You can find definition of interpolation type from "gsl_interp.h",
> > > and unfortunately it is not anything simple;
> > > 
> > > typedef struct {
> > > 
> > >   const char * name;
> > >   unsigned int min_size;
> > >   void *  (*alloc) (size_t size);
> > >   int     (*init)    (void *, const double xa[], const double ya[],
> > >   size_t
> > > 
> > > size);
> > > 
> > >   int     (*eval)    (const void *, const double xa[], const double
> > >   ya[],
> > > 
> > > size_t size, double x, gsl_interp_accel *, double * y);
> > > 
> > >   int     (*eval_deriv)  (const void *, const double xa[], const double
> > > 
> > > ya[], size_t size, double x, gsl_interp_accel *, double * y_p);
> > > 
> > >   int     (*eval_deriv2) (const void *, const double xa[], const double
> > > 
> > > ya[], size_t size, double x, gsl_interp_accel *, double * y_pp);
> > > 
> > >   int     (*eval_integ)  (const void *, const double xa[], const double
> > > 
> > > ya[], size_t size, gsl_interp_accel *, double a, double b, double *
> > > result); void    (*free)         (void *);
> > > 
> > > } gsl_interp_type;
> > > 
> > > GSL_VAR const gsl_interp_type * gsl_interp_cspline; * <-- this is used
> > > in example*
> > > 
> > > 
> > > Right now I don't know how to implement that reasonably in Gambas.
> > > There are at least three possibilities to overcome this problem:
> > > 
> > > 1. Hope that Benoit will implement new feature to use external
> > > structures. 2. Use C to write your own interface between GSL and
> > > Gambas. Perhaps easiest option.
> > > 3. Do not use GSL at all, and write what you need purely with Gambas.
> > > 
> > > That's all I can say...
> > > Also because you didn't specify what you need exactly, nor are you
> > > using Gambas 2 or 3.
> > > 
> > > Jussi
> 
> Hi,
> 
> I added a System.GetExternSymbol() method in the last revision so that you
> can get the address of the interpolation type structure.
> 
> You have to do something like that:
> 
> 	Dim gsl_interp_cspline As Pointer
> 
> 	gsl_interp_cspline = Pointer@(System.GetExternSymbol("libgsl",
> 		"gsl_interp_cspline"))
> 
> Maybe the Pointer@() is not needed, I don't know. The symbol can be
> directly the address of the structure (no Pointer@ needed), or a pointer
> to the address of the structure.
> 
> Try and tell me.
> 
> Regards,