Originální popis anglicky:
ilogb, ilogbf, ilogbl - get integer exponent of a floating point value
Návod, kniha: Linux Programmer's Manual
#include <math.h>
int ilogb(double x);
int ilogbf(float x);
int ilogbl(long double x);
Link with -lm.
These functions return the exponent part of their argument as a signed integer.
When no error occurs, these functions are equivalent to the corresponding
logb() functions, cast to (int). An error will occur for zero and
infinity and NaN, and possibly for overflow.
In order to check for errors, set
errno to zero and call
feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return,
if
errno is non-zero or
fetestexcept(FE_INVALID | FE_DIVBYZERO |
FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.
If an error occurs and
(math_errhandling & MATH_ERRNO) is non-zero,
then
errno is set to
EDOM. If an error occurs and
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid
floating-point exception is raised.
A domain error occurs when
x is zero or infinite (or too large, or too
small) or NaN. If
x is zero, the constant
FP_ILOGB0 is returned.
If
x is NaN, the constant
FP_ILOGBNAN is returned. If
x
is infinite (or too large), INT_MAX is returned. If
x is too small,
INT_MIN is returned.
ISO C99
log(3),
logb(3)
