# ilogb(3) [netbsd man page]

ILOGB(3)						   BSD Library Functions Manual 						  ILOGB(3)

NAME
ilogb, ilogbf, ilogbl -- an unbiased exponent LIBRARY
Math Library (libm, -lm) SYNOPSIS
#include <math.h> int ilogb(double x); int ilogbf(float x); int ilogbl(long double x); DESCRIPTION
The ilogb(), ilogbf(), and ilogbl() functions return the exponent of the non-zero real floating-point number x as a signed integer value. Formally the return value is the integral part of log_r | x |, where r is the radix of the machine's floating-point arithmetic defined by the FLT_RADIX constant in <float.h>. RETURN VALUES
As described above, upon successful completion, the functions return the exponent. Functionally this is the same as calling the correspond- ing logb(3) function and casting the return value to int. The following special cases may occur: 1. If x is zero, the value of FP_ILOGB0 is returned and a domain error occurs. 2. If x is infinite, a domain error occurs and the value of INT_MAX is returned. 3. If x is NaN, a domain error is raised and the value of FP_ILOGBNAN is returned. 4. If the correct value is outside the range of the return type, a domain error occurs but an unspecified value is returned. SEE ALSO
ilog2(3), logb(3), math(3) STANDARDS
The described functions conform to ISO/IEC 9899:1999 (``ISO C99''). BUGS
Neither FP_ILOGB0 nor FP_ILOGBNAN is defined currently in NetBSD. BSD
July 29, 2011 BSD

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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); 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 +infin- ity, 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 imple- ment 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
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