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Up: <a href="The-for-Statement.html" accesskey="u" rel="up">The for Statement</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<h4 class="subsection" id="Looping-Over-Structure-Elements-1"><span>10.5.1 Looping Over Structure Elements<a class="copiable-link" href="#Looping-Over-Structure-Elements-1"> &para;</a></span></h4>
<a class="index-entry-id" id="index-structure-elements_002c-looping-over"></a>
<a class="index-entry-id" id="index-looping-over-structure-elements"></a>

<p>A special form of the <code class="code">for</code> statement allows you to loop over all
the elements of a structure:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">for [ <var class="var">val</var>, <var class="var">key</var> ] = <var class="var">expression</var>
  <var class="var">body</var>
endfor
</pre></div></div>

<p>In this form of the <code class="code">for</code> statement, the value of <var class="var">expression</var>
must be a structure.  If it is, <var class="var">key</var> and <var class="var">val</var> are set to the
name of the element and the corresponding value in turn, until there are
no more elements.  For example:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">x.a = 1
x.b = [1, 2; 3, 4]
x.c = &quot;string&quot;
for [val, key] = x
  key
  val
endfor

     -| key = a
     -| val = 1
     -| key = b
     -| val =
     -|
     -|   1  2
     -|   3  4
     -|
     -| key = c
     -| val = string
</pre></div></div>

<p>The elements are not accessed in any particular order.  If you need to
cycle through the list in a particular way, you will have to use the
function <code class="code">fieldnames</code> and sort the list yourself.
</p>
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