[Bug-gsl] Catch-22 with interpolation objects

[Hendrik Weisser]

Hi!

For the creation of interpolation objects, a certain number of data 
points (varies depending on the interpolation type) is needed. The 
function "gsl_interp_min_size" can be used to find this number.

However, "gsl_interp_min_size" takes an interpolation object as 
argument, which can't be created with too few points. Thus, you can't 
use the function to check whether you have enough points to create the 
object, which kind of defeats its purpose.

I propose that "gsl_interp_min_size" be changed to the following:

unsigned int gsl_interp_min_size(const gsl_interp_type* T)
{
        return T->min_size;
}

It would be called with an interpolation type ("gsl_interp_linear" etc., 
same as "gsl_interp_alloc"), not an object, to get minimum size required 
for this type.


Best regards

Hendrik