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 <a name="Expression-trees"></a>
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 <p>
 Next: <a href="Statements.html#Statements" accesskey="n" rel="next">Statements</a>, Previous: <a href="Attributes.html#Attributes" accesskey="p" rel="prev">Attributes</a>, Up: <a href="GENERIC.html#GENERIC" accesskey="u" rel="up">GENERIC</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
 </div>
 <hr>
 <a name="Expressions-1"></a>
 <h3 class="section">10.6 Expressions</h3>
 <a name="index-expression"></a>
 <a name="index-TREE_005fTYPE-3"></a>
 <a name="index-TREE_005fOPERAND"></a>

 <p>The internal representation for expressions is for the most part quite
 straightforward.  However, there are a few facts that one must bear in
 mind.  In particular, the expression &ldquo;tree&rdquo; is actually a directed
 acyclic graph.  (For example there may be many references to the integer
 constant zero throughout the source program; many of these will be
 represented by the same expression node.)  You should not rely on
 certain kinds of node being shared, nor should you rely on certain kinds of
 nodes being unshared.
 </p>
 <p>The following macros can be used with all expression nodes:
 </p>
 <dl compact="compact">
 <dt><code>TREE_TYPE</code>
 <a name="index-TREE_005fTYPE-4"></a>
 </dt>
 <dd><p>Returns the type of the expression.  This value may not be precisely the
 same type that would be given the expression in the original program.
 </p></dd>
 </dl>

 <p>In what follows, some nodes that one might expect to always have type
 <code>bool</code> are documented to have either integral or boolean type.  At
 some point in the future, the C front end may also make use of this same
 intermediate representation, and at this point these nodes will
 certainly have integral type.  The previous sentence is not meant to
 imply that the C++ front end does not or will not give these nodes
 integral type.
 </p>
 <p>Below, we list the various kinds of expression nodes.  Except where
 noted otherwise, the operands to an expression are accessed using the
 <code>TREE_OPERAND</code> macro.  For example, to access the first operand to
 a binary plus expression <code>expr</code>, use:
 </p>
 <div class="smallexample">
 <pre class="smallexample">TREE_OPERAND (expr, 0)
 </pre></div>

 <p>As this example indicates, the operands are zero-indexed.
 </p>

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	<title>GNU Compiler Collection (GCC) Internals: Expression trees</title>

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	<a name="Expression-trees"></a>
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	<p>
	Next: <a href="Statements.html#Statements" accesskey="n" rel="next">Statements</a>, Previous: <a href="Attributes.html#Attributes" accesskey="p" rel="prev">Attributes</a>, Up: <a href="GENERIC.html#GENERIC" accesskey="u" rel="up">GENERIC</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
	</div>
	<hr>
	<a name="Expressions-1"></a>
	<h3 class="section">10.6 Expressions</h3>
	<a name="index-expression"></a>
	<a name="index-TREE_005fTYPE-3"></a>
	<a name="index-TREE_005fOPERAND"></a>

	<p>The internal representation for expressions is for the most part quite
	straightforward. However, there are a few facts that one must bear in
	mind. In particular, the expression “tree” is actually a directed
	acyclic graph. (For example there may be many references to the integer
	constant zero throughout the source program; many of these will be
	represented by the same expression node.) You should not rely on
	certain kinds of node being shared, nor should you rely on certain kinds of
	nodes being unshared.
	</p>
	<p>The following macros can be used with all expression nodes:
	</p>
	<dl compact="compact">
	<dt><code>TREE_TYPE</code>
	<a name="index-TREE_005fTYPE-4"></a>
	</dt>
	<dd><p>Returns the type of the expression. This value may not be precisely the
	same type that would be given the expression in the original program.
	</p></dd>
	</dl>

	<p>In what follows, some nodes that one might expect to always have type
	<code>bool</code> are documented to have either integral or boolean type. At
	some point in the future, the C front end may also make use of this same
	intermediate representation, and at this point these nodes will
	certainly have integral type. The previous sentence is not meant to
	imply that the C++ front end does not or will not give these nodes
	integral type.
	</p>
	<p>Below, we list the various kinds of expression nodes. Except where
	noted otherwise, the operands to an expression are accessed using the
	<code>TREE_OPERAND</code> macro. For example, to access the first operand to
	a binary plus expression <code>expr</code>, use:
	</p>
	<div class="smallexample">
	<pre class="smallexample">TREE_OPERAND (expr, 0)
	</pre></div>

	<p>As this example indicates, the operands are zero-indexed.
	</p>

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