ILOGB(3) BSD Library Functions Manual ILOGB(3)NAME
ilogb, ilogbf, ilogbl, logb, logbf, logbl — extract exponent
LIBRARY
Math Library (libm, -lm)
SYNOPSIS
#include <math.h>
int
ilogb(double x);
int
ilogbf(float x);
int
ilogbl(long double x);
double
logb(double x);
float
logbf(float x);
long double
logbl(long double x);
DESCRIPTIONilogb(), ilogbf() and ilogbl() return x's exponent in integer format.
ilogb(±∞) returns INT_MAX, ilogb(±NaN) returns FP_ILOGBNAN, and ilogb(0)
returns FP_ILOGB0.
logb(x), logbf(x), and logbl(x) return x's exponent in floating-point
format with the same precision as x. logb(±∞) returns +∞, and logb(0)
returns -∞ with a division by zero exception.
SEE ALSOfrexp(3), ieee(3), math(3), scalbn(3)STANDARDS
The ilogb(), ilogbf(), ilogbl(), logb(), logbf(), and logbl() routines
conform to ISO/IEC 9899:1999 (“ISO C99”). The latter three implement the
logb function recommended by IEEE Std 754-1985.
HISTORY
Function First Appeared In
logb() 4.3BSD
ilogb() FreeBSD 1.1.5
ilogbf() FreeBSD 2.0
logbf() FreeBSD 2.0
ilogbl() FreeBSD 5.4
logbl() FreeBSD 8.0
BSD December 16, 2007 BSD