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<title>The gsl_sf_result struct - GNU Scientific Library -- Reference Manual</title>
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<h3 class="section">7.2 The gsl_sf_result struct</h3>
<p><a name="index-gsl_005fsf_005fresult-239"></a><a name="index-gsl_005fsf_005fresult_005fe10-240"></a>
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 <samp><span class="file">gsl_sf_result.h</span></samp>.
<p>The <code>gsl_sf_result</code> struct contains value and error fields.
<pre class="example"> typedef struct
{
double val;
double err;
} gsl_sf_result;
</pre>
<p class="noindent">The field <var>val</var> contains the value and the field <var>err</var> contains
an estimate of the absolute error in the value.
<p>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
<code>gsl_sf_result_e10</code> struct contains value and error fields as well
as an exponent field such that the actual result is obtained as
<code>result * 10^(e10)</code>.
<pre class="example"> typedef struct
{
double val;
double err;
int e10;
} gsl_sf_result_e10;
</pre>
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