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ILOGB(3) BSD Library Functions Manual ILOGB(3)
ilogb, ilogbf, ilogbl -- an unbiased exponent
Math Library (libm, -lm)
ilogbl(long double x);
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 inte-
gral 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>.
As described above, upon successful completion, the functions return the exponent. Func-
tionally this is the same as calling the corresponding 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.
ilog2(3), logb(3), math(3)
The described functions conform to ISO/IEC 9899:1999 (``ISO C99'').
Neither FP_ILOGB0 nor FP_ILOGBNAN is defined currently in NetBSD.
BSD July 29, 2011 BSD
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