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fea681da | 1 | .\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>. |
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2 | .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk |
3 | .\" <mtk.manpages@gmail.com> | |
fea681da | 4 | .\" |
93015253 | 5 | .\" %%%LICENSE_START(VERBATIM) |
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6 | .\" Permission is granted to make and distribute verbatim copies of this |
7 | .\" manual provided the copyright notice and this permission notice are | |
8 | .\" preserved on all copies. | |
9 | .\" | |
10 | .\" Permission is granted to copy and distribute modified versions of this | |
11 | .\" manual under the conditions for verbatim copying, provided that the | |
12 | .\" entire resulting derived work is distributed under the terms of a | |
13 | .\" permission notice identical to this one. | |
c13182ef | 14 | .\" |
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15 | .\" Since the Linux kernel and libraries are constantly changing, this |
16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
17 | .\" responsibility for errors or omissions, or for damages resulting from | |
18 | .\" the use of the information contained herein. The author(s) may not | |
19 | .\" have taken the same level of care in the production of this manual, | |
20 | .\" which is licensed free of charge, as they might when working | |
21 | .\" professionally. | |
c13182ef | 22 | .\" |
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23 | .\" Formatted or processed versions of this manual, if unaccompanied by |
24 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 25 | .\" %%%LICENSE_END |
fea681da | 26 | .\" |
50831f9b | 27 | .TH CEIL 3 2010-09-20 "" "Linux Programmer's Manual" |
fea681da | 28 | .SH NAME |
c13182ef | 29 | ceil, ceilf, ceill \- ceiling function: smallest integral value not |
35478399 | 30 | less than argument |
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31 | .SH SYNOPSIS |
32 | .nf | |
33 | .B #include <math.h> | |
34 | .sp | |
35 | .BI "double ceil(double " x ); | |
36 | .br | |
37 | .BI "float ceilf(float " x ); | |
38 | .br | |
39 | .BI "long double ceill(long double " x ); | |
40 | .fi | |
41 | .sp | |
20c58d70 | 42 | Link with \fI\-lm\fP. |
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43 | .sp |
44 | .in -4n | |
45 | Feature Test Macro Requirements for glibc (see | |
46 | .BR feature_test_macros (7)): | |
47 | .in | |
48 | .sp | |
49 | .ad l | |
50 | .BR ceilf (), | |
51 | .BR ceill (): | |
b90c43a8 | 52 | .RS 4 |
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53 | _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE || |
54 | _POSIX_C_SOURCE\ >=\ 200112L; | |
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55 | .br |
56 | or | |
578d105f | 57 | .I cc\ -std=c99 |
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58 | .RE |
59 | .ad | |
fea681da | 60 | .SH DESCRIPTION |
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61 | These functions return the smallest integral value that is not less than |
62 | .IR x . | |
63 | ||
64 | For example, | |
65 | .IR ceil(0.5) | |
66 | is 1.0, and | |
67 | .IR ceil(\-0.5) | |
68 | is 0.0. | |
47297adb | 69 | .SH RETURN VALUE |
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70 | These functions return the ceiling of |
71 | .IR x . | |
72 | ||
73 | If \fIx\fP is integral, +0, \-0, NaN, or infinite, | |
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74 | \fIx\fP itself is returned. |
75 | .SH ERRORS | |
578d105f | 76 | No errors occur. |
efe294cb | 77 | POSIX.1-2001 documents a range error for overflows, but see NOTES. |
47297adb | 78 | .SH CONFORMING TO |
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79 | C99, POSIX.1-2001. |
80 | The variant returning | |
81 | .I double | |
82 | also conforms to | |
83 | SVr4, 4.3BSD, C89. | |
fea681da | 84 | .SH NOTES |
68e1685c | 85 | SUSv2 and POSIX.1-2001 contain text about overflow (which might set |
fea681da | 86 | .I errno |
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87 | to |
88 | .BR ERANGE , | |
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89 | or raise an |
90 | .B FE_OVERFLOW | |
91 | exception). | |
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92 | In practice, the result cannot overflow on any current machine, |
93 | so this error-handling stuff is just nonsense. | |
578d105f | 94 | .\" The POSIX.1-2001 APPLICATION USAGE SECTION discusses this point. |
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95 | (More precisely, overflow can happen only when the maximum value |
96 | of the exponent is smaller than the number of mantissa bits. | |
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97 | For the IEEE-754 standard 32-bit and 64-bit floating-point numbers |
98 | the maximum value of the exponent is 128 (respectively, 1024), | |
99 | and the number of mantissa bits is 24 (respectively, 53).) | |
100 | ||
101 | The integral value returned by these functions may be too large | |
102 | to store in an integer type | |
103 | .RI ( int , | |
104 | .IR long , | |
105 | etc.). | |
106 | To avoid an overflow, which will produce undefined results, | |
107 | an application should perform a range check on the returned value | |
108 | before assigning it to an integer type. | |
47297adb | 109 | .SH SEE ALSO |
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110 | .BR floor (3), |
111 | .BR lrint (3), | |
112 | .BR nearbyint (3), | |
113 | .BR rint (3), | |
114 | .BR round (3), | |
115 | .BR trunc (3) |