frexp(3)                   Library Functions Manual                   frexp(3)

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

LIBRARY
       Math library (libm, -lm)

SYNOPSIS
       #include <math.h>

       double frexp(double x, int *exp);
       float frexpf(float x, int *exp);
       long double frexpl(long double x, int *exp);

   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 exp.

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 exp.

       If x is a NaN, a NaN is returned, and the value of *exp is unspecified.

       If x is positive infinity (negative infinity), positive infinity
       (negative infinity) is returned, and the value of *exp 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 | MT-Safe |
       +--------------------------------------------+---------------+---------+
STANDARDS
       C11, POSIX.1-2008.

HISTORY
       C99, POSIX.1-2001.

       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 * 2^12 = 2560
           $ ./a.out -4
           frexp(-4, &e) = -0.5: -0.5 * 2^3 = -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 exp;

           x = strtod(argv[1], NULL);
           r = frexp(x, &exp);

           printf("frexp(%g, &e) = %g: %g * %d^%d = %g\n", x, r, r, 2, exp, x);
           exit(EXIT_SUCCESS);
       }

SEE ALSO
       ldexp(3), modf(3)

Linux man-pages 6.7               2024-01-29                          frexp(3)