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ILOGB(3)
ILOGB(3) FreeBSD Library Functions Manual ILOGB(3)

NAME

ilogb, ilogbf, ilogbl, logb, logbf, logblextract 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);

DESCRIPTION

ilogb(), ilogbf() and ilogbl() return x's exponent in integer format. ilogb( ±infinity) 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( ±infinity) returns +infinity, and logb( 0) returns -infinity with a division by zero exception.

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
December 16, 2007 FreeBSD