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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14 | .\" manual page may be incorrect or out-of-date.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 | .\" | |
50831f9b | 33 | .TH FREXP 3 2010-09-20 "" "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 |
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45 | .BI "long double frexpl(long double " x ", int *" exp ); |
46 | .fi | |
47 | .sp | |
20c58d70 | 48 | Link with \fI\-lm\fP. |
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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; | |
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61 | .br |
62 | or | |
6717c6ea | 63 | .I cc\ -std=c99 |
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64 | .RE |
65 | .ad | |
fea681da | 66 | .SH DESCRIPTION |
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67 | The |
68 | .BR frexp () | |
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69 | function is used to split the number |
70 | .I x | |
71 | into a | |
72 | normalized fraction and an exponent which is stored in | |
73 | .IR exp . | |
47297adb | 74 | .SH RETURN VALUE |
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75 | The |
76 | .BR frexp () | |
77 | function returns the normalized fraction. | |
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78 | If the argument |
79 | .I x | |
80 | is not zero, | |
81 | the normalized fraction is | |
82 | .I x | |
83 | times a power of two, | |
a2af275c | 84 | and its absolute value is always in the range 1/2 (inclusive) to |
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85 | 1 (exclusive), that is, [0.5,1). |
86 | ||
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87 | If |
88 | .I x | |
89 | is zero, then the normalized fraction is | |
90 | zero and zero is stored in | |
91 | .IR exp . | |
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92 | |
93 | If | |
94 | .I x | |
95 | is a NaN, | |
96 | a NaN is returned, and the value of | |
97 | .I *exp | |
98 | is unspecified. | |
99 | ||
100 | If | |
101 | .I x | |
102 | is positive infinity (negative infinity), | |
103 | positive infinity (negative infinity) is returned, and the value of | |
104 | .I *exp | |
105 | is unspecified. | |
106 | .SH ERRORS | |
107 | No errors occur. | |
47297adb | 108 | .SH CONFORMING TO |
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109 | C99, POSIX.1-2001. |
110 | The variant returning | |
111 | .I double | |
112 | also conforms to | |
113 | SVr4, 4.3BSD, C89. | |
fea681da | 114 | .SH EXAMPLE |
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115 | The program below produces results such as the following: |
116 | .sp | |
117 | .nf | |
118 | .in +4n | |
119 | .RB "$" " ./a.out 2560" | |
120 | frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560 | |
121 | .RB "$" " ./a.out \-4" | |
c3074d70 | 122 | frexp(\-4, &e) = \-0.5: \-0.5 * 2^3 = \-4 |
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123 | .in |
124 | .fi | |
125 | .SS Program source | |
d84d0300 | 126 | \& |
fea681da | 127 | .nf |
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128 | #include <math.h> |
129 | #include <float.h> | |
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130 | #include <stdio.h> |
131 | #include <stdlib.h> | |
132 | ||
133 | int | |
134 | main(int argc, char *argv[]) | |
135 | { | |
136 | double x, r; | |
137 | int exp; | |
138 | ||
139 | x = strtod(argv[1], NULL); | |
140 | r = frexp(x, &exp); | |
141 | ||
39ad75ab | 142 | printf("frexp(%g, &e) = %g: %g * %d^%d = %g\\n", |
7295b7ed | 143 | x, r, r, FLT_RADIX, exp, x); |
a2af275c | 144 | exit(EXIT_SUCCESS); |
c54ed37e | 145 | } |
fea681da | 146 | .fi |
47297adb | 147 | .SH SEE ALSO |
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148 | .BR ldexp (3), |
149 | .BR modf (3) |