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<h4 class="subsection">4.2.5 Elif</h4>
<p><a name="index-g_t_0023elif-91"></a>One common case of nested conditionals is used to check for more than two
possible alternatives. For example, you might have
<pre class="smallexample"> #if X == 1
...
#else /* X != 1 */
#if X == 2
...
#else /* X != 2 */
...
#endif /* X != 2 */
#endif /* X != 1 */
</pre>
<p>Another conditional directive, ‘<samp><span class="samp">#elif</span></samp>’, allows this to be
abbreviated as follows:
<pre class="smallexample"> #if X == 1
...
#elif X == 2
...
#else /* X != 2 and X != 1*/
...
#endif /* X != 2 and X != 1*/
</pre>
<p>‘<samp><span class="samp">#elif</span></samp>’ stands for “else if”. Like ‘<samp><span class="samp">#else</span></samp>’, it goes in the
middle of a conditional group and subdivides it; it does not require a
matching ‘<samp><span class="samp">#endif</span></samp>’ of its own. Like ‘<samp><span class="samp">#if</span></samp>’, the ‘<samp><span class="samp">#elif</span></samp>’
directive includes an expression to be tested. The text following the
‘<samp><span class="samp">#elif</span></samp>’ is processed only if the original ‘<samp><span class="samp">#if</span></samp>’-condition
failed and the ‘<samp><span class="samp">#elif</span></samp>’ condition succeeds.
<p>More than one ‘<samp><span class="samp">#elif</span></samp>’ can go in the same conditional group. Then
the text after each ‘<samp><span class="samp">#elif</span></samp>’ is processed only if the ‘<samp><span class="samp">#elif</span></samp>’
condition succeeds after the original ‘<samp><span class="samp">#if</span></samp>’ and all previous
‘<samp><span class="samp">#elif</span></samp>’ directives within it have failed.
<p>‘<samp><span class="samp">#else</span></samp>’ is allowed after any number of ‘<samp><span class="samp">#elif</span></samp>’ directives, but
‘<samp><span class="samp">#elif</span></samp>’ may not follow ‘<samp><span class="samp">#else</span></samp>’.
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