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man:frexpf

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

NAME

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

SYNOPSIS

     #include <math.h>
     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 feature_test_macros(7)):
     frexpf(), frexpl():
         _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
             || /* Since glibc 2.19: */ _DEFAULT_SOURCE
             || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

     These functions are used to split the number x into a normalized  frac-
     tion 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 (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).
     allbox; lbw27 lb lb  l  l  l.   Interface Attribute Value  T{  frexp(),
     frexpf(), frexpl() T}   Thread safety  MT-Safe

CONFORMING TO

     C99, POSIX.1-2001, POSIX.1-2008.
     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  <math.h>  #include  <float.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, FLT_RADIX, exp, x);
         exit(EXIT_SUCCESS); }

SEE ALSO

     ldexp(3), modf(3)

COLOPHON

     This  page  is  part of release 4.16 of the Linux man-pages project.  A
     description of the project, information about reporting bugs,  and  the
     latest     version     of     this    page,    can    be    found    at
     https://www.kernel.org/doc/man-pages/.
                                2017-09-15                          FREXP(3)
/data/webs/external/dokuwiki/data/pages/man/frexpf.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

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