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<title>GNU Scientific Library – Reference Manual: The gsl_sf_result struct</title>
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<a name="The-gsl_005fsf_005fresult-struct"></a>
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<p>
Next: <a href="Special-Function-Modes.html#Special-Function-Modes" accesskey="n" rel="next">Special Function Modes</a>, Previous: <a href="Special-Function-Usage.html#Special-Function-Usage" accesskey="p" rel="previous">Special Function Usage</a>, Up: <a href="Special-Functions.html#Special-Functions" accesskey="u" rel="up">Special Functions</a> [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
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<a name="The-gsl_005fsf_005fresult-struct-1"></a>
<h3 class="section">7.2 The gsl_sf_result struct</h3>
<a name="index-gsl_005fsf_005fresult"></a>
<a name="index-gsl_005fsf_005fresult_005fe10"></a>
<a name="index-gsl_005fsf_005fresult-1"></a>
<a name="index-gsl_005fsf_005fresult_005fe10-1"></a>
<p>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>gsl_sf_result.h</samp>.
</p>
<p>The <code>gsl_sf_result</code> struct contains value and error fields.
</p>
<div class="example">
<pre class="example">typedef struct
{
double val;
double err;
} gsl_sf_result;
</pre></div>
<p>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>
<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>.
</p>
<div class="example">
<pre class="example">typedef struct
{
double val;
double err;
int e10;
} gsl_sf_result_e10;
</pre></div>
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