/* evaluate a function discarding the status value in a modifiable way */

#define EVAL_RESULT(fn) \

   gsl_sf_result result; \

   int status = fn; \

   if (status != GSL_SUCCESS) { \

     GSL_ERROR_VAL(#fn, status, result.val); \

   } ; \

   return result.val;

#define EVAL_DOUBLE(fn) \

   int status = fn; \

   if (status != GSL_SUCCESS) { \

     GSL_ERROR_VAL(#fn, status, result); \

   } ; \

   return result;