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Node:<a name="If%20Function">If Function</a>,
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<h3 class="section">The <code>if</code> Function</h3>

   <p>The <code>if</code> function provides support for conditional expansion in a
functional context (as opposed to the GNU <code>make</code> makefile
conditionals such as <code>ifeq</code> (see <a href="Conditional-Syntax.html#Conditional%20Syntax">Syntax of Conditionals</a>).

   <p>An <code>if</code> function call can contain either two or three arguments:

<pre class="example">     $(if <var>condition</var>,<var>then-part</var>[,<var>else-part</var>])
     </pre>

   <p>The first argument, <var>condition</var>, first has all preceding and
trailing whitespace stripped, then is expanded.  If it expands to any
non-empty string, then the condition is considered to be true.  If it
expands to an empty string, the condition is considered to be false.

   <p>If the condition is true then the second argument, <var>then-part</var>, is
evaluated and this is used as the result of the evaluation of the entire
<code>if</code> function.

   <p>If the condition is false then the third argument, <var>else-part</var>, is
evaluated and this is the result of the <code>if</code> function.  If there is
no third argument, the <code>if</code> function evaluates to nothing (the
empty string).

   <p>Note that only one of the <var>then-part</var> or the <var>else-part</var> will be
evaluated, never both.  Thus, either can contain side-effects (such as
<code>shell</code> function calls, etc.)

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