FREXP(3) Linux Programmer's Manual FREXP(3)

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

SYNOPSIS
       #include 

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

       Link with -lm.

   Feature Test Macro Requirements for glibc (see featuretestmacros(7)):

       frexpf(), frexpl():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 600 ||
           ISOC99SOURCE || POSIXCSOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION
       The  frexp()  function  is used to split the number x into a normalized
       fraction and an exponent which is stored in exp.

RETURN VALUE
       The frexp() function returns 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  (exclu‐
       sive), 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 (nega‐
       tive 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 │
       └────────────────────────────┴───────────────┴─────────┘
CONFORMING TO
       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4,
       4.3BSD, C89.

EXAMPLE
       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 
       #include 
       #include 
       #include 

       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, FLTRADIX, exp, x);
           exit(EXITSUCCESS);
       }

SEE ALSO
       ldexp(3), modf(3)

COLOPHON
       This  page  is  part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



                                  2010-09-20                          FREXP(3)