1ILOGB(3)                   Linux Programmer's Manual                  ILOGB(3)
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NAME

6       ilogb, ilogbf, ilogbl - get integer exponent of a floating point value
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SYNOPSIS

9       #include <math.h>
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11       int ilogb(double x);
12       int ilogbf(float x);
13       int ilogbl(long double x);
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15       Link with -lm.
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DESCRIPTION

18       These  functions return the exponent part of their argument as a signed
19       integer. When no error occurs, these functions are  equivalent  to  the
20       corresponding logb() functions, cast to (int).  An error will occur for
21       zero and infinity and NaN, and possibly for overflow.
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ERRORS

24       In order to check for errors, set errno to  zero  and  call  feclearex‐
25       cept(FE_ALL_EXCEPT) before calling these functions. On return, if errno
26       is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO |  FE_OVERFLOW  |
27       FE_UNDERFLOW) is non-zero, an error has occurred.
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29       If  an  error  occurs  and (math_errhandling & MATH_ERRNO) is non-zero,
30       then errno is set to EDOM.  If an error occurs and (math_errhandling  &
31       MATH_ERREXCEPT)  is non-zero, then the invalid floating-point exception
32       is raised.
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34       A domain error occurs when x is zero or infinite (or too large, or  too
35       small) or NaN.  If x is zero, the constant FP_ILOGB0 is returned.  If x
36       is NaN, the constant FP_ILOGBNAN is returned.  If x is infinite (or too
37       large), INT_MAX is returned.  If x is too small, INT_MIN is returned.
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CONFORMING TO

40       C99
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SEE ALSO

43       log(3), logb(3)
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47                                  2004-10-31                          ILOGB(3)
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