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| <h3 class="section">6.7 Conditionals with Omitted Operands</h3> |
| |
| <p><a name="index-conditional-expressions_002c-extensions-2430"></a><a name="index-omitted-middle_002doperands-2431"></a><a name="index-middle_002doperands_002c-omitted-2432"></a><a name="index-extensions_002c-_0040code_007b_003f_003a_007d-2433"></a><a name="index-g_t_0040code_007b_003f_003a_007d-extensions-2434"></a> |
| The middle operand in a conditional expression may be omitted. Then |
| if the first operand is nonzero, its value is the value of the conditional |
| expression. |
| |
| <p>Therefore, the expression |
| |
| <pre class="smallexample"> x ? : y |
| </pre> |
| <p class="noindent">has the value of <code>x</code> if that is nonzero; otherwise, the value of |
| <code>y</code>. |
| |
| <p>This example is perfectly equivalent to |
| |
| <pre class="smallexample"> x ? x : y |
| </pre> |
| <p><a name="index-side-effect-in-_0040code_007b_003f_003a_007d-2435"></a><a name="index-g_t_0040code_007b_003f_003a_007d-side-effect-2436"></a>In this simple case, the ability to omit the middle operand is not |
| especially useful. When it becomes useful is when the first operand does, |
| or may (if it is a macro argument), contain a side effect. Then repeating |
| the operand in the middle would perform the side effect twice. Omitting |
| the middle operand uses the value already computed without the undesirable |
| effects of recomputing it. |
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