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1 | .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
2 | .\" | |
93015253 | 3 | .\" %%%LICENSE_START(VERBATIM) |
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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. | |
7 | .\" | |
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. | |
c13182ef | 12 | .\" |
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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14 | .\" manual page may be incorrect or out-of-date.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 | |
19 | .\" professionally. | |
c13182ef | 20 | .\" |
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21 | .\" Formatted or processed versions of this manual, if unaccompanied by |
22 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 23 | .\" %%%LICENSE_END |
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24 | .\" |
25 | .\" References consulted: | |
26 | .\" Linux libc source code | |
27 | .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) | |
28 | .\" 386BSD man pages | |
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) | |
32 | .\" | |
c73595c2 | 33 | .TH FREXP 3 2015-04-19 "" "Linux Programmer's Manual" |
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34 | .SH NAME |
35 | frexp, frexpf, frexpl \- convert floating-point number to fractional | |
36 | and integral components | |
37 | .SH SYNOPSIS | |
38 | .nf | |
39 | .B #include <math.h> | |
40 | .sp | |
41 | .BI "double frexp(double " x ", int *" exp ); | |
d39541ec | 42 | .br |
fea681da | 43 | .BI "float frexpf(float " x ", int *" exp ); |
d39541ec | 44 | .br |
fea681da MK |
45 | .BI "long double frexpl(long double " x ", int *" exp ); |
46 | .fi | |
47 | .sp | |
20c58d70 | 48 | Link with \fI\-lm\fP. |
6717c6ea MK |
49 | .sp |
50 | .in -4n | |
51 | Feature Test Macro Requirements for glibc (see | |
52 | .BR feature_test_macros (7)): | |
53 | .in | |
54 | .sp | |
55 | .ad l | |
56 | .BR frexpf (), | |
57 | .BR frexpl (): | |
b90c43a8 | 58 | .RS 4 |
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59 | _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE || |
60 | _POSIX_C_SOURCE\ >=\ 200112L; | |
b90c43a8 MK |
61 | .br |
62 | or | |
6717c6ea | 63 | .I cc\ -std=c99 |
b90c43a8 MK |
64 | .RE |
65 | .ad | |
fea681da | 66 | .SH DESCRIPTION |
5600f73a | 67 | These functions are used to split the number |
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68 | .I x |
69 | into a | |
70 | normalized fraction and an exponent which is stored in | |
71 | .IR exp . | |
47297adb | 72 | .SH RETURN VALUE |
5600f73a | 73 | These functions return the normalized fraction. |
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74 | If the argument |
75 | .I x | |
76 | is not zero, | |
77 | the normalized fraction is | |
78 | .I x | |
79 | times a power of two, | |
a2af275c | 80 | and its absolute value is always in the range 1/2 (inclusive) to |
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81 | 1 (exclusive), that is, [0.5,1). |
82 | ||
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83 | If |
84 | .I x | |
85 | is zero, then the normalized fraction is | |
86 | zero and zero is stored in | |
87 | .IR exp . | |
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88 | |
89 | If | |
90 | .I x | |
91 | is a NaN, | |
92 | a NaN is returned, and the value of | |
93 | .I *exp | |
94 | is unspecified. | |
95 | ||
96 | If | |
97 | .I x | |
98 | is positive infinity (negative infinity), | |
99 | positive infinity (negative infinity) is returned, and the value of | |
100 | .I *exp | |
101 | is unspecified. | |
102 | .SH ERRORS | |
103 | No errors occur. | |
7e9ee9a4 | 104 | .SH ATTRIBUTES |
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105 | For an explanation of the terms used in this section, see |
106 | .BR attributes (7). | |
107 | .TS | |
108 | allbox; | |
109 | lbw27 lb lb | |
110 | l l l. | |
111 | Interface Attribute Value | |
112 | T{ | |
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113 | .BR frexp (), |
114 | .BR frexpf (), | |
7e9ee9a4 | 115 | .BR frexpl () |
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116 | T} Thread safety MT-Safe |
117 | .TE | |
47297adb | 118 | .SH CONFORMING TO |
9a74e018 | 119 | C99, POSIX.1-2001, POSIX.1-2008. |
e05e3635 | 120 | |
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121 | The variant returning |
122 | .I double | |
123 | also conforms to | |
124 | SVr4, 4.3BSD, C89. | |
fea681da | 125 | .SH EXAMPLE |
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126 | The program below produces results such as the following: |
127 | .sp | |
128 | .nf | |
129 | .in +4n | |
130 | .RB "$" " ./a.out 2560" | |
131 | frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560 | |
132 | .RB "$" " ./a.out \-4" | |
c3074d70 | 133 | frexp(\-4, &e) = \-0.5: \-0.5 * 2^3 = \-4 |
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134 | .in |
135 | .fi | |
136 | .SS Program source | |
d84d0300 | 137 | \& |
fea681da | 138 | .nf |
fea681da MK |
139 | #include <math.h> |
140 | #include <float.h> | |
a2af275c MK |
141 | #include <stdio.h> |
142 | #include <stdlib.h> | |
143 | ||
144 | int | |
145 | main(int argc, char *argv[]) | |
146 | { | |
147 | double x, r; | |
148 | int exp; | |
149 | ||
150 | x = strtod(argv[1], NULL); | |
151 | r = frexp(x, &exp); | |
152 | ||
39ad75ab | 153 | printf("frexp(%g, &e) = %g: %g * %d^%d = %g\\n", |
7295b7ed | 154 | x, r, r, FLT_RADIX, exp, x); |
a2af275c | 155 | exit(EXIT_SUCCESS); |
c54ed37e | 156 | } |
fea681da | 157 | .fi |
47297adb | 158 | .SH SEE ALSO |
fea681da MK |
159 | .BR ldexp (3), |
160 | .BR modf (3) |