NAME
ilogb() — returns an unbiased exponent
SYNOPSIS
#include <math.h>
int ilogb(double x);
DESCRIPTION
The
ilogb()
function returns the exponent part of
x.
Formally, the return value is the integral part of
log base
r
of
|x|
as a signed integral value, for nonzero
x,
where
r
is the radix of the machine's floating point arithmetic.
The argument
x
is a double-precision floating-point value.
Note:
ilogb(x)
is equivalent to
(int)logb(x)
for all values of
x
except NaN, ±INFINITY, and zero.
The ISO/ANSI C committee has approved the
ilogb()
function for inclusion in the C9X draft standard.
To use this function, compile either with the default
-Ae
option or with the
-Aa
and
-D_HPUX_SOURCE
options. Make sure your program includes
<math.h>.
Link in the math library by specifying
-lm
on the compiler or linker command line.
RETURN VALUE
If
x
is NaN,
ilogb()
returns
INT_MIN.
If
x
is ±INFINITY,
ilogb()
returns
INT_MAX.
If
x
is zero,
ilogb()
returns
INT_MIN.
ERRORS
No errors are defined.
STANDARDS CONFORMANCE
ilogb(): XPG4.2
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