1RINT(3P) POSIX Programmer's Manual RINT(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 rint, rintf, rintl — round-to-nearest integral value
13
15 #include <math.h>
16 double rint(double x);
18 float rintf(float x);
19 long double rintl(long double x);
20
22 The functionality described on this reference page is aligned with the
23 ISO C standard. Any conflict between the requirements described here
24 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
25 defers to the ISO C standard.
26 These functions shall return the integral value (represented as a dou‐
28 ble) nearest x in the direction of the current rounding mode. The cur‐
29 rent rounding mode is implementation-defined.
30 If the current rounding mode rounds toward negative infinity, then
32 rint() shall be equivalent to floor(). If the current rounding mode
33 rounds toward positive infinity, then rint() shall be equivalent to
34 ceil(). If the current rounding mode rounds towards zero, then rint()
35 shall be equivalent to trunc(). If the current rounding mode rounds
36 towards nearest, then rint() differs from round() in that halfway cases
37 are rounded to even rather than away from zero.
38 These functions differ from the nearbyint(), nearbyintf(), and nearby‐
40 intl() functions only in that they may raise the inexact floating-point
41 exception if the result differs in value from the argument.
42 An application wishing to check for error situations should set errno
44 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
45 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
46 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
47 occurred.
48
50 Upon successful completion, these functions shall return the integer
51 (represented as a double precision number) nearest x in the direction
52 of the current rounding mode. The result shall have the same sign as
53 x.
54 If x is NaN, a NaN shall be returned.
56 If x is ±0 or ±Inf, x shall be returned.
58
60 No errors are defined.
61 The following sections are informative.
63
65 None.
66
68 The integral value returned by these functions need not be expressible
69 as an intmax_t. The return value should be tested before assigning it
70 to an integer type to avoid the undefined results of an integer over‐
71 flow.
72
74 None.
75
77 None.
78
80 abs(), ceil(), feclearexcept(), fetestexcept(), floor(), isnan(), near‐
81 byint()
82 The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
84 Error Conditions for Mathematical Functions, <math.h>
85
87 Portions of this text are reprinted and reproduced in electronic form
88 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
89 table Operating System Interface (POSIX), The Open Group Base Specifi‐
90 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
91 Electrical and Electronics Engineers, Inc and The Open Group. In the
92 event of any discrepancy between this version and the original IEEE and
93 The Open Group Standard, the original IEEE and The Open Group Standard
94 is the referee document. The original Standard can be obtained online
95 at http://www.opengroup.org/unix/online.html .
96 Any typographical or formatting errors that appear in this page are
98 most likely to have been introduced during the conversion of the source
99 files to man page format. To report such errors, see https://www.ker‐
100 nel.org/doc/man-pages/reporting_bugs.html .
101IEEE/The Open Group 2017 RINT(3P)