ilogb, ilogbf, ilogbl — get integer exponent of a floating point value
#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(3) 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.
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