DragonFly On-Line Manual Pages


ILOGB(3)	      DragonFly 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);

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.

SEE ALSO

frexp(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() DragonFly 2.13 logbl() DragonFly 2.13 DragonFly 3.7 December 21, 2011 DragonFly 3.7