man3/rint.3

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  27 .TH RINT 3  2017-09-15 "" "Linux Programmer's Manual"
  28 .SH NAME
  29 nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl \- round
  30 to nearest integer
  31 .SH SYNOPSIS
  32 .nf
  33 .B #include <math.h>
  34 .PP
  35 .BI "double nearbyint(double " x );
  36 .BI "float nearbyintf(float " x );
  37 .BI "long double nearbyintl(long double " x );
  38 .PP
  39 .BI "double rint(double " x );
  40 .BI "float rintf(float " x );
  41 .BI "long double rintl(long double " x );
  42 .fi
  43 .PP
  44 Link with \fI\-lm\fP.
  45 .PP
  46 .in -4n
  47 Feature Test Macro Requirements for glibc (see
  48 .BR feature_test_macros (7)):
  49 .in
  50 .PP
  51 .ad l
  52 .BR nearbyint (),
  53 .BR nearbyintf (),
  54 .BR nearbyintl ():
  55 .RS 4
  56 _POSIX_C_SOURCE\ >=\ 200112L || _ISOC99_SOURCE
  57 .RE
  58 .br
  59 .BR rint ():
  60 .RS 4
  61 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  62     || _XOPEN_SOURCE\ >=\ 500
  63 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  64     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  65     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  66 .RE
  67 .br
  68 .BR rintf (),
  69 .BR rintl ():
  70 .RS 4
  71 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  72     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  73     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  74 .RE
  75 .ad b
  76 .SH DESCRIPTION
  77 The
  78 .BR nearbyint (),
  79 .BR nearbyintf (),
  80 and
  81 .BR nearbyintl ()
  82 functions round their argument to an integer value in floating-point
  83 format, using the current rounding direction (see
  84 .BR fesetround (3))
  85 and without raising the
  86 .I inexact
  87 exception.
  88 When the current rounding direction is to nearest, these
  89 functions round halfway cases to the even integer in accordance with
  90 IEEE-754.
  91 .PP
  92 The
  93 .BR rint (),
  94 .BR rintf (),
  95 and
  96 .BR rintl ()
  97 functions do the same, but will raise the
  98 .I inexact
  99 exception
 100 .RB ( FE_INEXACT ,
 101 checkable via
 102 .BR fetestexcept (3))
 103 when the result differs in value from the argument.
 104 .SH RETURN VALUE
 105 These functions return the rounded integer value.
 106 .PP
 107 If
 108 .I x
 109 is integral, +0, \-0, NaN, or infinite,
 110 .I x
 111 itself is returned.
 112 .SH ERRORS
 113 No errors occur.
 114 POSIX.1-2001 documents a range error for overflows, but see NOTES.
 115 .SH ATTRIBUTES
 116 For an explanation of the terms used in this section, see
 117 .BR attributes (7).
 118 .TS
 119 allbox;
 120 lbw26 lb lb
 121 l l l.
 122 Interface       Attribute       Value
 123 T{
 124 .BR nearbyint (),
 125 .BR nearbyintf (),
 126 .br
 127 .BR nearbyintl (),
 128 .BR rint (),
 129 .br
 130 .BR rintf (),
 131 .BR rintl ()
 132 T}      Thread safety   MT-Safe
 133 .TE
 134 .SH CONFORMING TO
 135 C99, POSIX.1-2001, POSIX.1-2008.
 136 .SH NOTES
 137 SUSv2 and POSIX.1-2001 contain text about overflow (which might set
 138 .I errno
 139 to
 140 .BR ERANGE ,
 141 or raise an
 142 .B FE_OVERFLOW
 143 exception).
 144 In practice, the result cannot overflow on any current machine,
 145 so this error-handling stuff is just nonsense.
 146 (More precisely, overflow can happen only when the maximum value
 147 of the exponent is smaller than the number of mantissa bits.
 148 For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
 149 the maximum value of the exponent is 128 (respectively, 1024),
 150 and the number of mantissa bits is 24 (respectively, 53).)
 151 .PP
 152 If you want to store the rounded value in an integer type,
 153 you probably want to use one of the functions described in
 154 .BR lrint (3)
 155 instead.
 156 .SH SEE ALSO
 157 .BR ceil (3),
 158 .BR floor (3),
 159 .BR lrint (3),
 160 .BR round (3),
 161 .BR trunc (3)