1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
3 .\" Permission is granted to make and distribute verbatim copies of this
4 .\" manual provided the copyright notice and this permission notice are
5 .\" preserved on all copies.
7 .\" Permission is granted to copy and distribute modified versions of this
8 .\" manual under the conditions for verbatim copying, provided that the
9 .\" entire resulting derived work is distributed under the terms of a
10 .\" permission notice identical to this one.
12 .\" Since the Linux kernel and libraries are constantly changing, this
13 .\" manual page may be incorrect or out-of-date. The author(s) assume no
14 .\" responsibility for errors or omissions, or for damages resulting from
15 .\" the use of the information contained herein. The author(s) may not
16 .\" have taken the same level of care in the production of this manual,
17 .\" which is licensed free of charge, as they might when working
20 .\" Formatted or processed versions of this manual, if unaccompanied by
21 .\" the source, must acknowledge the copyright and authors of this work.
23 .\" References consulted:
24 .\" Linux libc source code
25 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
27 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
28 .\" Modified 2002-07-27 by Walter Harms
29 .\" (walter.harms@informatik.uni-oldenburg.de)
31 .\" Japanese Version Copyright (c) 1997 YOSHINO Takashi
32 .\" all rights reserved.
33 .\" Translated 1997-01-21, YOSHINO Takashi <yoshino@civil.jcn.nihon-u.ac.jp>
34 .\" Updated 2003-10-15, Kentaro Shirakata <argrath@ub32.org>
35 .\" Updated 2005-11-19, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
37 .TH FREXP 3 2010-09-20 "" "Linux Programmer's Manual"
40 .\"O frexp, frexpf, frexpl \- convert floating-point number to fractional
41 .\"O and integral components
42 frexp, frexpf, frexpl \- ÉâÆ°¾®¿ôÅÀ¼Â¿ô¤ò¾®¿ôÀ®Ê¬¤ÈÀ°¿ôÀ®Ê¬¤ËÊÑ´¹¤¹¤ë
48 .BI "double frexp(double " x ", int *" exp );
50 .BI "float frexpf(float " x ", int *" exp );
52 .BI "long double frexpl(long double " x ", int *" exp );
55 .\"O Link with \fI\-lm\fP.
56 \fI\-lm\fP ¤Ç¥ê¥ó¥¯¤¹¤ë¡£
59 .\"O Feature Test Macro Requirements for glibc (see
60 .\"O .BR feature_test_macros (7)):
61 glibc ¸þ¤±¤Îµ¡Ç½¸¡ºº¥Þ¥¯¥í¤ÎÍ×·ï
62 .RB ( feature_test_macros (7)
70 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
71 _POSIX_C_SOURCE\ >=\ 200112L;
81 .\"O function is used to split the number \fIx\fP into a
82 .\"O normalized fraction and an exponent which is stored in \fIexp\fP.
84 ´Ø¿ô¤ÏÉâÆ°¾®¿ôÅÀ¼Â¿ô \fIx\fP ¤òÀµµ¬²½¾®¿ô¤È»Ø¿ô¤Ëʬ²ò¤·¡¢
85 »Ø¿ô¤ò *\fIexp\fP ¤Ë³ÊǼ¤¹¤ë¡£
86 .\"O .SH "RETURN VALUE"
90 .\"O function returns the normalized fraction.
91 .\"O If the argument \fIx\fP is not zero,
92 .\"O the normalized fraction is \fIx\fP times a power of two,
93 .\"O and its absolute value is always in the range 1/2 (inclusive) to
94 .\"O 1 (exclusive), that is, [0.5,1).
96 ´Ø¿ô¤ÏÀµµ¬²½¾®¿ô¤òÊÖ¤¹¡£
97 °ú¿ô \fIx\fP ¤¬¥¼¥í¤Ç¤Ê¤¤¾ì¹ç¡¢¤³¤ÎÀµµ¬²½¾®¿ô¤Ï
98 \fIx\fP ¤Ë 2 ¤ÎÎß¾è¤ò¾è¤¸¤¿¤â¤Î¤Ç¤¢¤ê¡¢¤½¤ÎÀäÂÐÃͤÏ
99 ¾ï¤Ë 1/2 °Ê¾å 1 ̤Ëþ¡¢¤Ä¤Þ¤ê [0.5,1) ¤È¤Ê¤ë¡£
101 .\"O If \fIx\fP is zero, then the normalized fraction is
102 .\"O zero and zero is stored in \fIexp\fP.
103 \fIx\fP ¤¬¥¼¥í¤Î¾ì¹ç¡¢Àµµ¬²½¾®¿ô¤Ï¥¼¥í¤Ë¤Ê¤ê
104 *\fIexp\fP ¤Ë¤Ï¥¼¥í¤¬³ÊǼ¤µ¤ì¤ë¡£
109 .\"O a NaN is returned, and the value of
113 ¤¬ NaN ¤Î¾ì¹ç¡¢NaN ¤¬ÊÖ¤µ¤ì¤ë¡£
119 .\"O is positive infinity (negative infinity),
120 .\"O positive infinity (negative infinity) is returned, and the value of
124 ¤¬Àµ¤Î̵¸ÂÂç (Éé¤Î̵¸ÂÂç) ¤Î¾ì¹ç¡¢
125 Àµ¤Î̵¸ÂÂç (Éé¤Î̵¸ÂÂç) ¤¬ÊÖ¤µ¤ì¤ë¡£
130 .\"O No errors occur.
132 .\"O .SH "CONFORMING TO"
135 .\"O The variant returning
137 .\"O also conforms to
138 .\"O SVr4, 4.3BSD, C89.
140 ÈǤδؿô¤Ï SVr4, 4.3BSD, C89 ¤Ë¤â½àµò¤·¤Æ¤¤¤ë¡£
143 .\"O The program below produces results such as the following:
144 ¤³¤Î¥×¥í¥°¥é¥à¤ò¼Â¹Ô¤¹¤ë¤È°Ê²¼¤Î¤è¤¦¤Ê·ë²Ì¤È¤Ê¤ë:
148 .RB "$" " ./a.out 2560"
149 frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
150 .RB "$" " ./a.out \-4"
151 frexp(\-4, &e) = \-0.5: \-0.5 * 2^3 = \-4
154 .\"O .SS Program source
155 .SS ¥×¥í¥°¥é¥à¤Î¥½¡¼¥¹
164 main(int argc, char *argv[])
169 x = strtod(argv[1], NULL);
172 printf("frexp(%g, &e) = %g: %g * %d^%d = %g\\n",
173 x, r, r, FLT_RADIX, exp, x);