GNU Scientific Library Reference Manual - Third Edition (v1.12)by M. Galassi, J. Davies, J. Theiler, B. Gough, G. Jungman, P. Alken, M. Booth, F. Rossi Paperback (6"x9"), 592 pages, 60 figures ISBN 0954612078 RRP £24.95 ($39.95) |

## 7.2 The gsl_sf_result struct

The error handling form of the special functions always calculate an
error estimate along with the value of the result. Therefore,
structures are provided for amalgamating a value and error estimate.
These structures are declared in the header file `‘gsl_sf_result.h’`.

The `gsl_sf_result`

struct contains value and error fields.

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

The field `val` contains the value and the field `err` contains
an estimate of the absolute error in the value.

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 in order to save the result from
exceeding the dynamic range of the built-in types. The
`gsl_sf_result_e10`

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;

ISBN 0954612078 | GNU Scientific Library Reference Manual - Third Edition (v1.12) | See the print edition |