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frexp

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

frexp, frexpf, frexpl - convert floatin-point number to fractional and integral components

LIBRARY

Math library (libm,~-lm)

SYNOPSIS

#include <math.h>
double frexp(double x, int *e);
float frexpf(float x, int *e);
long double frexpl(long double x, int *e);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)): frexpf(), frexpl():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

These functions are used to split the number x into a normalized fraction and an exponent which is stored in e.

RETURN VALUE

These functions return the normalized fraction. If the argument x is not zero, the normalized fraction is x times a power of two, and its absolute value is always in the range 1/2 (inclusive) to 1 (exclusive), that is, [0.5,1). If x is zero, then the normalized fraction is zero and zero is stored in e. If x is a NaN, a NaN is returned, and the value of *e is unspecified. If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned, and the value of *e is unspecified.

ERRORS

No errors occur.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
frexp(), frexpf(), frexpl()	Thread safety	M-Safe

STANDARDS

C11, POSIX.-2008.

HISTORY

C99, POSIX.-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.

EXAMPLES

The program below produces results such as the following: $ ./a.out 2560 frexp(2560, &e) = 0.625: 0.625 * 2[ha]12 = 2560 $ ./a.out -4 frexp(-4, &e) = -0.5: -0.5 * 2[ha]3 = -4

Program source

#include <float.h> #include <math.h> #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) {
    double x, r;
    int e;
    x = strtod(argv[1], NULL);
    r = frexp(x, &e);
    printf("frexp(%g, &e) = %g: %g * %d[ha]%d = %g[rs]n", x, r, r, 2, e, x);
    exit(EXIT_SUCCESS); }

Index

Program source

SEE ALSO