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| <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. |
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| <tr><td align="left" valign="top">• <a href="Constant-expressions.html#Constant-expressions" accesskey="1">Constants</a>:</td><td> </td><td align="left" valign="top"> |
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| <tr><td align="left" valign="top">• <a href="Unary-and-Binary-Expressions.html#Unary-and-Binary-Expressions" accesskey="3">Unary and Binary Expressions</a>:</td><td> </td><td align="left" valign="top"> |
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| <tr><td align="left" valign="top">• <a href="Vectors.html#Vectors" accesskey="4">Vectors</a>:</td><td> </td><td align="left" valign="top"> |
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