code>, you would do:
</p><div class="example">
<pre class="example"> call fftw_execute_dft(plan, in, out)
</pre></div>
<span id="index-fftw_005fexecute_005fdft-3"></span>

<p>There are a few things to be careful of, however:
</p>
<ul>
<li> <span id="index-fftw_005fexecute_005fdft_005fr2c-2"></span>
<span id="index-fftw_005fexecute_005fdft_005fc2r-1"></span>
<span id="index-fftw_005fexecute_005fr2r-1"></span>
You must use the correct type of execute function, matching the way
the plan was created.  Complex D