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| <h3 class="section">1.28 <code>ilogb</code>, <code>ilogbf</code>—get exponent of floating-point number</h3> |
| |
| <p><a name="index-ilogb-75"></a><a name="index-ilogbf-76"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <math.h> |
| int ilogb(double <var>val</var>); |
| int ilogbf(float <var>val</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| |
| <p>All nonzero, normal numbers can be described as <var>m</var> * |
| 2**<var>p</var>. <code>ilogb</code> and <code>ilogbf</code> examine the argument |
| <var>val</var>, and return <var>p</var>. The functions <code>frexp</code> and |
| <code>frexpf</code> are similar to <code>ilogb</code> and <code>ilogbf</code>, but also |
| return <var>m</var>. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| |
| <p><code>ilogb</code> and <code>ilogbf</code> return the power of two used to form the |
| floating-point argument. |
| If <var>val</var> is <code>0</code>, they return <code>FP_ILOGB0</code>. |
| If <var>val</var> is infinite, they return <code>INT_MAX</code>. |
| If <var>val</var> is NaN, they return <code>FP_ILOGBNAN</code>. |
| (<code>FP_ILOGB0</code> and <code>FP_ILOGBNAN</code> are defined in math.h, but in turn are |
| defined as INT_MIN or INT_MAX from limits.h. The value of FP_ILOGB0 may be |
| either INT_MIN or -INT_MAX. The value of FP_ILOGBNAN may be either INT_MAX or |
| INT_MIN.) |
| |
| <!-- The bugs might not be worth noting, given the mass non-C99/POSIX --> |
| <!-- behavior of much of the Newlib math library. --> |
| <!-- BUGS --> |
| <!-- On errors, errno is not set per C99 and POSIX requirements even if --> |
| <!-- (math_errhandling & MATH_ERRNO) is non-zero. --> |
| <p><br> |
| <strong>Portability</strong><br> |
| C99, POSIX |
| |
| <p><br> |
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