1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
'\" t
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" References consulted:
.\" Linux libc source code
.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\" 386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-07-27 by Walter Harms
.\" (walter.harms@informatik.uni-oldenburg.de)
.\"
.TH frexp 3 2023-03-30 "Linux man-pages 6.04"
.SH NAME
frexp, frexpf, frexpl \- convert floating-point number to fractional
and integral components
.SH LIBRARY
Math library
.RI ( libm ", " \-lm )
.SH SYNOPSIS
.nf
.B #include <math.h>
.PP
.BI "double frexp(double " x ", int *" exp );
.BI "float frexpf(float " x ", int *" exp );
.BI "long double frexpl(long double " x ", int *" exp );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR frexpf (),
.BR frexpl ():
.nf
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
These functions are used to split the number
.I x
into a
normalized fraction and an exponent which is stored in
.IR exp .
.SH RETURN VALUE
These functions return the normalized fraction.
If the argument
.I x
is not zero,
the normalized fraction is
.I 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).
.PP
If
.I x
is zero, then the normalized fraction is
zero and zero is stored in
.IR exp .
.PP
If
.I x
is a NaN,
a NaN is returned, and the value of
.I *exp
is unspecified.
.PP
If
.I x
is positive infinity (negative infinity),
positive infinity (negative infinity) is returned, and the value of
.I *exp
is unspecified.
.SH ERRORS
No errors occur.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.BR frexp (),
.BR frexpf (),
.BR frexpl ()
T} Thread safety MT-Safe
.TE
.hy
.ad
.sp 1
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.PP
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH EXAMPLES
The program below produces results such as the following:
.PP
.in +4n
.EX
.RB "$" " ./a.out 2560"
frexp(2560, &e) = 0.625: 0.625 * 2\[ha]12 = 2560
.RB "$" " ./a.out \-4"
frexp(\-4, &e) = \-0.5: \-0.5 * 2\[ha]3 = \-4
.EE
.in
.SS Program source
\&
.\" SRC BEGIN (frexp.c)
.EX
#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\[ha]%d = %g\en",
x, r, r, FLT_RADIX, exp, x);
exit(EXIT_SUCCESS);
}
.EE
.\" SRC END
.SH SEE ALSO
.BR ldexp (3),
.BR modf (3)
|
