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
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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14 .\" manual page may be incorrect or out-of-date.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
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18 .\" which is licensed free of charge, as they might when working
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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 2010-09-20 "" "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 \fIx\fP into a
70 normalized fraction and an exponent which is stored in \fIexp\fP.
74 function returns the normalized fraction.
75 If the argument \fIx\fP is not zero,
76 the normalized fraction is \fIx\fP times a power of two,
77 and its absolute value is always in the range 1/2 (inclusive) to
78 1 (exclusive), that is, [0.5,1).
80 If \fIx\fP is zero, then the normalized fraction is
81 zero and zero is stored in \fIexp\fP.
86 a NaN is returned, and the value of
92 is positive infinity (negative infinity),
93 positive infinity (negative infinity) is returned, and the value of
100 The variant returning
105 The program below produces results such as the following:
109 .RB "$" " ./a.out 2560"
110 frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
111 .RB "$" " ./a.out \-4"
112 frexp(\-4, &e) = \-0.5: \-0.5 * 2^3 = \-4
124 main(int argc, char *argv[])
129 x = strtod(argv[1], NULL);
132 printf("frexp(%g, &e) = %g: %g * %d^%d = %g\\n",
133 x, r, r, FLT_RADIX, exp, x);