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<title>GNU Scientific Library &ndash; Reference Manual: Error Reporting Examples</title>

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<a name="Error-Reporting-Examples"></a>
<div class="header">
<p>
Previous: <a href="Using-GSL-error-reporting-in-your-own-functions.html#Using-GSL-error-reporting-in-your-own-functions" accesskey="p" rel="previous">Using GSL error reporting in your own functions</a>, Up: <a href="Error-Handling.html#Error-Handling" accesskey="u" rel="up">Error Handling</a> &nbsp; [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Examples"></a>
<h3 class="section">3.5 Examples</h3>

<p>Here is an example of some code which checks the return value of a
function where an error might be reported,
</p>
<div class="example">
<pre class="example">#include &lt;stdio.h&gt;
#include &lt;gsl/gsl_errno.h&gt;
#include &lt;gsl/gsl_fft_complex.h&gt;

...
  int status;
  size_t n = 37;

  gsl_set_error_handler_off();

  status = gsl_fft_complex_radix2_forward (data, stride, n);

  if (status) {
    if (status == GSL_EINVAL) {
       fprintf (stderr, &quot;invalid argument, n=%d\n&quot;, n);
    } else {
       fprintf (stderr, &quot;failed, gsl_errno=%d\n&quot;, 
                        status);
    }
    exit (-1);
  }
...
</pre></div>

<p>The function <code>gsl_fft_complex_radix2</code> only accepts integer lengths
which are a power of two.  If the variable <code>n</code> is not a power of
two then the call to the library function will return <code>GSL_EINVAL</code>,
indicating that the length argument is invalid.  The function call to
<code>gsl_set_error_handler_off</code> stops the default error handler from
aborting the program.  The <code>else</code> clause catches any other possible
errors.
</p>




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