1LROUND(3P) POSIX Programmer's Manual LROUND(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
13 lround, lroundf, lroundl — round to nearest integer value
14
16 #include <math.h>
17 long lround(double x);
19 long lroundf(float x);
20 long lroundl(long double x);
21
23 The functionality described on this reference page is aligned with the
24 ISO C standard. Any conflict between the requirements described here
25 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
26 defers to the ISO C standard.
27 These functions shall round their argument to the nearest integer
29 value, rounding halfway cases away from zero, regardless of the current
30 rounding direction.
31 An application wishing to check for error situations should set errno
33 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
34 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
35 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
36 occurred.
37
39 Upon successful completion, these functions shall return the rounded
40 integer value.
41 If x is NaN, a domain error shall occur and an unspecified value is
43 returned.
44 If x is +Inf, a domain error shall occur and an unspecified value is
46 returned.
47 If x is −Inf, a domain error shall occur and an unspecified value is
49 returned.
50 If the correct value is positive and too large to represent as a long,
52 an unspecified value shall be returned. On systems that support the
53 IEC 60559 Floating-Point option, a domain shall occur; otherwise, a
54 domain error may occur.
55 If the correct value is negative and too large to represent as a long,
57 an unspecified value shall be returned. On systems that support the
58 IEC 60559 Floating-Point option, a domain shall occur; otherwise, a
59 domain error may occur.
60
62 These functions shall fail if:
63 Domain Error
65 The x argument is NaN or ±Inf, or the correct value is not
66 representable as an integer.
67 If the integer expression (math_errhandling & MATH_ERRNO)
69 is non-zero, then errno shall be set to [EDOM]. If the
70 integer expression (math_errhandling & MATH_ERREXCEPT) is
71 non-zero, then the invalid floating-point exception shall
72 be raised.
73 These functions may fail if:
75 Domain Error
77 The correct value is not representable as an integer.
78 If the integer expression (math_errhandling & MATH_ERRNO)
80 is non-zero, then errno shall be set to [EDOM]. If the
81 integer expression (math_errhandling & MATH_ERREXCEPT) is
82 non-zero, then the invalid floating-point exception shall
83 be raised.
84 The following sections are informative.
86
88 None.
89
91 On error, the expressions (math_errhandling & MATH_ERRNO) and
92 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
93 at least one of them must be non-zero.
94
96 These functions differ from the lrint() functions in the default round‐
97 ing direction, with the lround() functions rounding halfway cases away
98 from zero and needing not to raise the inexact floating-point exception
99 for non-integer arguments that round to within the range of the return
100 type.
101
103 None.
104
106 feclearexcept(), fetestexcept(), llround()
107 The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of
109 Error Conditions for Mathematical Functions, <math.h>
110
112 Portions of this text are reprinted and reproduced in electronic form
113 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
114 -- Portable Operating System Interface (POSIX), The Open Group Base
115 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
116 cal and Electronics Engineers, Inc and The Open Group. (This is
117 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
118 event of any discrepancy between this version and the original IEEE and
119 The Open Group Standard, the original IEEE and The Open Group Standard
120 is the referee document. The original Standard can be obtained online
121 at http://www.unix.org/online.html .
122 Any typographical or formatting errors that appear in this page are
124 most likely to have been introduced during the conversion of the source
125 files to man page format. To report such errors, see https://www.ker‐
126 nel.org/doc/man-pages/reporting_bugs.html .
127IEEE/The Open Group 2013 LROUND(3P)