convert double (class::*)(const gsl_vector*, void*) to double (*)(const_gsl vector*,void*) [duplicate]

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• Passing pointer-to-member-function as pointer-to-function 1 answer

I'm minimizing a function min_fun(const gsl_vector*, void*) with the gsl minimizer gsl_multimin_fminimizer_nmsimplex2. To give this one the function to minimize you define gsl_multimin_function minex_func;

and then minex_func.f = min_fun ; minex_func.n = 3; (The numbers of variables to minimize and the number of elements of const gsl_vector) minex_func.par = par; (the void* in which you give the function all parameters which are constant for one function call)

When I had both in my main file (the gsl minimization directly in my main() and min_fun as a function defined in my main file) it all worked like this. Now I want to take this routine in a Function in a Class called Potential so that I can just have a one line call for the minimizing process in my main file.

So I now define Potential::Minimize() in which I have the exact same call as before for the minimzation. I also define Potential::min_fun(const gsl_vector*, void*) which is the same as the min_fun before.

Depending on my versions for minex_func.f = I get different errors :

minex_func.f = Potential::min_fun ; -> this one leads to error: cannot convert ‘Potential::min_fun’ from type ‘double (Potential::)(const gsl_vector*, void*)’ to type ‘double ()(const gsl_vector, void*)’

minex_func.f = &Potential::min_fun; -> Here we get error: cannot convert ‘double (Potential::)(const gsl_vector, void*)’ to ‘double ()(const gsl_vector, void*)’

minex_func.f = min_fun; Here we get error: cannot convert ‘Potential::min_fun’ from type ‘double (Potential::)(const gsl_vector*, void*)’ to type ‘double ()(const gsl_vector, void*)

If I use Potential *modfunc = new Potential;

and then

minex_func.f = modfunc->min_fun; I get error: cannot convert ‘Potential::min_fun’ from type ‘double (Potential::)(const gsl_vector*, void*)’ to type ‘double ()(const gsl_vector, void*)’

Can someone explain me how to get it to work and what the difference is between the Statement directly in the main file and in the Class Definition?

Cheers, Bär.