Commit | Line | Data |
---|---|---|
af359dea C |
1 | .\" Copyright (c) 1985, 1991 Regents of the University of California. |
2 | .\" All rights reserved. | |
3 | .\" | |
c0567266 KB |
4 | .\" Redistribution and use in source and binary forms, with or without |
5 | .\" modification, are permitted provided that the following conditions | |
6 | .\" are met: | |
7 | .\" 1. Redistributions of source code must retain the above copyright | |
8 | .\" notice, this list of conditions and the following disclaimer. | |
9 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
10 | .\" notice, this list of conditions and the following disclaimer in the | |
11 | .\" documentation and/or other materials provided with the distribution. | |
12 | .\" 3. All advertising materials mentioning features or use of this software | |
13 | .\" must display the following acknowledgement: | |
14 | .\" This product includes software developed by the University of | |
15 | .\" California, Berkeley and its contributors. | |
16 | .\" 4. Neither the name of the University nor the names of its contributors | |
17 | .\" may be used to endorse or promote products derived from this software | |
18 | .\" without specific prior written permission. | |
19 | .\" | |
20 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
21 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
22 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
23 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
24 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
25 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
26 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
27 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
28 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
29 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
30 | .\" SUCH DAMAGE. | |
af359dea C |
31 | .\" |
32 | .\" @(#)rint.3 5.1 (Berkeley) 5/2/91 | |
33 | .\" | |
34 | .Dd May 2, 1991 | |
35 | .Dt RINT 3 | |
36 | .Os | |
37 | .Sh NAME | |
38 | .Nm rint | |
39 | .Nd and round-to-closest integer functions | |
40 | .Sh SYNOPSIS | |
41 | .Fd #include <math.h> | |
42 | .Ft double | |
43 | .Fn rint "double x" | |
44 | .Sh DESCRIPTION | |
45 | The | |
46 | .Fn rint | |
47 | function finds the integer (represented as a double precision number) | |
48 | nearest to | |
49 | .Fa x | |
50 | in the direction of the prevailing rounding mode. | |
51 | .Sh NOTES | |
52 | On a | |
53 | .Tn VAX , | |
54 | .Fn rint x | |
55 | is equivalent to adding half to the magnitude | |
56 | and then rounding towards zero. | |
57 | .Pp | |
58 | In the default rounding mode, to nearest, | |
59 | on a machine that conforms to | |
60 | .Tn IEEE | |
61 | 754, | |
62 | .Fn rint x | |
63 | is the integer nearest | |
64 | .Fa x | |
65 | with the additional stipulation | |
66 | that if | |
67 | .Li |rint(x)\-x|=1/2 | |
68 | then | |
69 | .Fn rint x | |
70 | is even. | |
71 | Other rounding modes can make | |
72 | .Fn rint | |
73 | act like | |
74 | .Fn floor , | |
75 | or like | |
76 | .Fn ceil , | |
77 | or round towards zero. | |
78 | .Pp | |
79 | Another way to obtain an integer near | |
80 | .Fa x | |
81 | is to declare (in C) | |
82 | .Bd -literal -offset indent | |
83 | double x;\0\0\0\0 int k;\0\0\0\0k\0=\0x; | |
84 | .Ed | |
85 | .Pp | |
86 | Most C compilers round | |
87 | .Fa x | |
88 | towards 0 to get the integer | |
89 | .Fa k , | |
90 | but | |
91 | some do otherwise. | |
92 | If in doubt, use | |
93 | .Fn floor , | |
94 | .Fn ceil , | |
95 | or | |
96 | .Fn rint | |
97 | first, whichever you intend. | |
98 | Also note that, if x is larger than | |
99 | .Fa k | |
100 | can accommodate, the value of | |
101 | .Fa k | |
102 | and the presence or absence of an integer overflow are hard to | |
103 | predict. | |
104 | .Sh SEE ALSO | |
105 | .Xr abs 3 , | |
106 | .Xr fabs 3 , | |
107 | .Xr ceil 3 , | |
108 | .Xr floor 3 , | |
109 | .Xr ieee 3 , | |
110 | .Xr math 3 | |
111 | .Sh HISTORY | |
112 | A | |
113 | .Fn rint | |
114 | function appeared in | |
115 | .At v6 . |