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Manual Pages  — ILOGB

NAME

ilogb, ilogbf, ilogbl, logb, logbf, logbl – extract exponent

CONTENTS

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, Ns, 's, exponent in integer format. ilogb(±∞) returns INT_MAX, ilogb(±NaN) returns FP_ILOGBNAN, and ilogb() returns FP_ILOGB0.

logb(x), logbf(x), and logbl(x) return x, Ns, 's, exponent in floating-point format with the same precision as x. logb(±∞) returns +∞, and logb() returns -∞ 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 -ieee754.

HISTORY

Function First Appeared In
logb()
  BSD 4.3
ilogb()
  FreeBSD 1.1.5
ilogbf()
  FreeBSD 2.0
logbf()
  FreeBSD 2.0
ilogbl()
  FreeBSD 5.4
logbl()
  FreeBSD 8.0

ILOGB (3) December 16, 2007

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C isn't that hard: void (*(*f[])())() defines f as an array of unspecified size, of pointers to functions that return pointers to functions that return void