netbsd man page for ilogb

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