The gsl_sf_result struct
========================

Almost all the special functions calculate an error estimate along with the value of the result. Therefore, structures are provided for amalgating a value and error estimate.

The gsl_sf_result struct contains value and error fields.

     typedef struct
     {
       double val;
       double err;
     } gsl_sf_result;

In some cases, an overflow or underflow can be detected and handled by a function. In this case, it may be possible to return a scaling exponent as well as an error/value pair. The gsl_sf_result struct contains value and error fields as well as an exponent field such that the actual result is obtained as result * 10^(e10).

     typedef struct
     {
       double val;
       double err;
       int    e10;
     } gsl_sf_result_e10;