1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
3 .\" %%%LICENSE_START(VERBATIM)
4 .\" Permission is granted to make and distribute verbatim copies of this
5 .\" manual provided the copyright notice and this permission notice are
6 .\" preserved on all copies.
8 .\" Permission is granted to copy and distribute modified versions of this
9 .\" manual under the conditions for verbatim copying, provided that the
10 .\" entire resulting derived work is distributed under the terms of a
11 .\" permission notice identical to this one.
13 .\" Since the Linux kernel and libraries are constantly changing, this
14 .\" manual page may be incorrect or out-of-date. The author(s) assume no
15 .\" responsibility for errors or omissions, or for damages resulting from
16 .\" the use of the information contained herein. The author(s) may not
17 .\" have taken the same level of care in the production of this manual,
18 .\" which is licensed free of charge, as they might when working
21 .\" Formatted or processed versions of this manual, if unaccompanied by
22 .\" the source, must acknowledge the copyright and authors of this work.
25 .\" References consulted:
26 .\" Linux libc source code
27 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
29 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
30 .\" Modified 2002-07-27 by Walter Harms
31 .\" (walter.harms@informatik.uni-oldenburg.de)
33 .TH FREXP 3 2013-08-06 "" "Linux Programmer's Manual"
35 frexp, frexpf, frexpl \- convert floating-point number to fractional
36 and integral components
41 .BI "double frexp(double " x ", int *" exp );
43 .BI "float frexpf(float " x ", int *" exp );
45 .BI "long double frexpl(long double " x ", int *" exp );
51 Feature Test Macro Requirements for glibc (see
52 .BR feature_test_macros (7)):
59 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
60 _POSIX_C_SOURCE\ >=\ 200112L;
69 function is used to split the number
72 normalized fraction and an exponent which is stored in
77 function returns the normalized fraction.
81 the normalized fraction is
84 and its absolute value is always in the range 1/2 (inclusive) to
85 1 (exclusive), that is, [0.5,1).
89 is zero, then the normalized fraction is
90 zero and zero is stored in
96 a NaN is returned, and the value of
102 is positive infinity (negative infinity),
103 positive infinity (negative infinity) is returned, and the value of
109 .SS Multithreading (see pthreads(7))
115 functions are thread-safe.
118 The variant returning
123 The program below produces results such as the following:
127 .RB "$" " ./a.out 2560"
128 frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
129 .RB "$" " ./a.out \-4"
130 frexp(\-4, &e) = \-0.5: \-0.5 * 2^3 = \-4
142 main(int argc, char *argv[])
147 x = strtod(argv[1], NULL);
150 printf("frexp(%g, &e) = %g: %g * %d^%d = %g\\n",
151 x, r, r, FLT_RADIX, exp, x);