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| <h3 class="section">1.51 <code>signbit</code>–Does floating-point number have negative sign?</h3> |
| |
| <p><a name="index-signbit-139"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <math.h> |
| int signbit(real-floating <var>x</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| The <code>signbit</code> macro determines whether the sign of its argument value is |
| negative. The macro reports the sign of all values, including infinities, |
| zeros, and NaNs. If zero is unsigned, it is treated as positive. As shown in |
| the synopsis, the argument is "real-floating," meaning that any of the real |
| floating-point types (float, double, etc.) may be given to it. |
| |
| <p>Note that because of the possibilities of signed 0 and NaNs, the expression |
| "<var>x</var> < 0.0" does not give the same result as <code>signbit</code> in all cases. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| The <code>signbit</code> macro returns a nonzero value if and only if the sign of its |
| argument value is negative. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| C99, POSIX. |
| |
| <p><br> |
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