frexp(3) - Linux manual page (original) (raw)

frexp(3) Library Functions Manual frexp(3)

NAME top

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

LIBRARY top

   Math library (_libm_, _-lm_)

SYNOPSIS top

   **#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 top

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

RETURN VALUE top

   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 top

   No errors occur.

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **frexp**(), **frexpf**(), **frexpl**()          │ Thread safety │ MT-Safe │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   C11, POSIX.1-2008.

HISTORY top

   C99, POSIX.1-2001.

   The variant returning _double_ also conforms to SVr4, 4.3BSD, C89.

EXAMPLES top

   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 top

   [ldexp(3)](../man3/ldexp.3.html), [modf(3)](../man3/modf.3.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 frexp(3)

Pages that refer to this page:ldexp(3), modf(3)