pass parameters in GSL integration

struct my_f_params {int a; int b;}; 
gsl_function F1; 
struct my_f_params alpha = {2,2};               
F1.function = &f1; 
F1.params = & alpha;

struct my_f_params * params = (struct my_f_params *)p;
int n = (params->a);
int m = (params->b);

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double params[] = { y, z };
F.params = params;

double y = ((double *)params)[0];
double z =  *((double *)p+1);