1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
3 .\" <mtk.manpages@gmail.com>
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
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 1995-08-14 by Arnt Gulbrandsen <agulbra@troll.no>
31 .\" Modified 2002-07-27 by Walter Harms
32 .\" (walter.harms@informatik.uni-oldenburg.de)
34 .\" Japanese Version Copyright (c) 2004-2005 Yuichi SATO
35 .\" all rights reserved.
36 .\" Translated 2004-08-20, Yuichi SATO <ysato444@yahoo.co.jp>
37 .\" Updated & Modified 2005-01-16, Yuichi SATO
38 .\" Updated & Modified 2005-09-06, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
39 .\" Updated 2008-09-16, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
41 .TH LOG2 3 2008-08-11 "" "Linux Programmer's Manual"
44 .\"O log2, log2f, log2l \- base-2 logarithmic function
45 log2, log2f, log2l \- Ä줬 2 ¤ÎÂпô´Ø¿ô
51 .BI "double log2(double " x );
53 .BI "float log2f(float " x );
55 .BI "long double log2l(long double " x );
58 .\"O Link with \fI\-lm\fP.
59 \fI\-lm\fP ¤Ç¥ê¥ó¥¯¤¹¤ë¡£
62 .\"O Feature Test Macro Requirements for glibc (see
63 .\"O .BR feature_test_macros (7)):
64 glibc ¸þ¤±¤Îµ¡Ç½¸¡ºº¥Þ¥¯¥í¤ÎÍ×·ï
65 .RB ( feature_test_macros (7)
73 _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
80 .\"O function returns the base 2 logarithm of \fIx\fP.
82 ´Ø¿ô¤ÏÄì¤ò 2 ¤È¤¹¤ë \fIx\fP ¤ÎÂпô¤òÊÖ¤¹¡£
85 .\"O On success, these functions return the base 2 logarithm of
87 À®¸ù¤¹¤ë¤È¡¢¤³¤ì¤é¤Î´Ø¿ô¤Ï
89 ¤ÎÄì¤ò 2 ¤È¤¹¤ëÂпô¤òÊÖ¤¹¡£
91 .\"O For special cases, including where
93 .\"O is 0, 1, negative, infinity, or NaN, see
96 ¤¬ 0¡¢1¡¢É顢̵¸ÂÂç¡¢NaN ¤Ê¤É¤Î¤µ¤Þ¤¶¤Þ¤ÊÆÃÊ̤ʾõ¶·¤Ë¤Ä¤¤¤Æ¤Ï¡¢
102 .\"O .BR math_error (7)
103 .\"O for information on how to determine whether an error has occurred
104 .\"O when calling these functions.
105 ¤³¤ì¤é¤Î´Ø¿ô¤ò¸Æ¤Ó½Ð¤·¤¿ºÝ¤Ë¥¨¥é¡¼¤¬È¯À¸¤·¤¿¤«¤ÎȽÄêÊýË¡¤Ë¤Ä¤¤¤Æ¤Î¾ðÊó¤Ï
109 .\"O For a discussion of the errors that can occur for these functions, see
111 ¤³¤ì¤é¤Î´Ø¿ô¤ÇȯÀ¸¤¹¤ë¥¨¥é¡¼¤Ë¤Ä¤¤¤Æ¤Ï¡¢
116 .\"O These functions first appeared in glibc in version 2.1.
117 ¤³¤ì¤é¤Î´Ø¿ô¤Ï glibc ¥Ð¡¼¥¸¥ç¥ó 2.1 ¤Ç½é¤á¤ÆÅо줷¤¿¡£
118 .\"O .SH "CONFORMING TO"
121 .\"O The variant returning
123 .\"O also conforms to
124 .\"O SVr4, 4.3BSD, C89.
126 ÈǤδؿô¤Ï SVr4, 4.3BSD, C89 ¤Ë¤â½àµò¤·¤Æ¤¤¤ë¡£