Re: [Help-gsl] Use of Macro GSL_FN_EVAL

[Jerome BENOIT]

Hello,

have you tried:

GSL_FN_EVAL(&F,x)


hth,
Jerome

Luis Dias wrote:
> Hi,
>
> Does anybody have an example of how to use the macro GSL_FN_EVAL  :
>
> #define GSL_FN_EVAL(F,x)
>         (*((F)->function))(x,(F)->params)
>
>
> (to evaluate a gsl_function).
> For instance, say I have the code that's in the manual (just changed 
> some variable names for clarity):
>
> =============================================
>
>     struct three_numbers { double a; double b; double c; };
>         double my_f (double x, void *p) {
>        struct three_numbers *params1 = (struct three_numbers *)p;
>        double a1 = (params1->a);
>        double b1 = (params1->b);
>        double c1 = (params1->c);
>            return  (a1 * x + b1) * x + c1;
>     }
>         gsl_function F;
>     struct three_numbers params_of_my_f = { 3.0, 2.0, 1.0 };
>         F.function = &my_f;
>     F.params = &params_of_my_f;
>
>
> =============================================
>
>     How do I use GSL_FN_EVAL in this example, to evaluate, say F(10.0) 
> and get 321.0?
> (it works by doing, say,double aux=my_f(10.0,&params_of_my_f) but can I 
> do it using F?)
>
>    Thanks!
>    Luis
>
>
>
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--
Jerome BENOIT
jgmbenoit_at_mailsnare_dot_net