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Up: <a href="The-for-Statement.html" accesskey="u" rel="up">The for Statement</a> [<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"> ¶</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 = "string"
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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