typedef double (*praxis_func)(int n, const double *x, void *f_data);
-nlopt_result praxis_(double *t0, double machep, double *h0,
+nlopt_result praxis_(double t0, double machep, double h0,
int n, double *x, praxis_func f, void *f_data,
nlopt_stopping *stop, double *minf);