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<h4 class="subsection" id="if_002delse-1">5.23.3 if-else</h4>
<a class="index-entry-id" id="index-if_002delse"></a>
<dl class="first-deffn">
<dt class="deffn" id="index-_002eie"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.ie</code></strong> <var class="def-var-arguments">cond-expr anything</var><a class="copiable-link" href='#index-_002eie'> ¶</a></span></dt>
<dd><a class="index-entry-id" id="index-ie"></a>
</dd><dt class="deffnx def-cmd-deffn" id="index-_002eel"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.el</code></strong> <var class="def-var-arguments">anything</var><a class="copiable-link" href='#index-_002eel'> ¶</a></span></dt>
<dd><a class="index-entry-id" id="index-el"></a>
<p>Use the <code class="code">ie</code> and <code class="code">el</code> requests to write an if-then-else. The
first request is the “if” part and the latter is the “else” part.
Unusually among programming languages, any number of non-conditional
requests may be interposed between the <code class="code">ie</code> branch and the
<code class="code">el</code> branch.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">.nr a 0
.ie \na a is non-zero.
.nr a +1
.el a was not positive but is now \na.
⇒ a was not positive but is now 1.
</pre></div></div>
<p>Another way in which <code class="code">el</code> is an ordinary request is that it does
not lexically “bind” more tightly to its <code class="code">ie</code> counterpart than it
does to any other request. This fact can surprise C programmers.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">.nr a 1
.nr z 0
.ie \nz \
. ie \na a is true
. el a is false
.el z is false
error→ warning: unbalanced 'el' request
⇒ a is false
</pre></div></div>
<p>To conveniently nest conditionals, keep reading.
</p>
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