man3/rint.3

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  27 .TH RINT 3  2016-03-15 "" "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 .br
  37 .BI "float nearbyintf(float " x );
  38 .br
  39 .BI "long double nearbyintl(long double " x );
  40 .PP
  41 .BI "double rint(double " x );
  42 .br
  43 .BI "float rintf(float " x );
  44 .br
  45 .BI "long double rintl(long double " x );
  46 .fi
  47 .PP
  48 Link with \fI\-lm\fP.
  49 .PP
  50 .in -4n
  51 Feature Test Macro Requirements for glibc (see
  52 .BR feature_test_macros (7)):
  53 .in
  54 .PP
  55 .ad l
  56 .BR nearbyint (),
  57 .BR nearbyintf (),
  58 .BR nearbyintl ():
  59 .RS 4
  60 _POSIX_C_SOURCE\ >=\ 200112L || _ISOC99_SOURCE
  61 .RE
  62 .br
  63 .BR rint ():
  64 .RS 4
  65 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  66     || _XOPEN_SOURCE\ >=\ 500
  67 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  68     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  69     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  70 .RE
  71 .br
  72 .BR rintf (),
  73 .BR rintl ():
  74 .RS 4
  75 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  76     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  77     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  78 .RE
  79 .ad b
  80 .SH DESCRIPTION
  81 The
  82 .BR nearbyint (),
  83 .BR nearbyintf (),
  84 and
  85 .BR nearbyintl ()
  86 functions round their argument to an integer value in floating-point
  87 format, using the current rounding direction (see
  88 .BR fesetround (3))
  89 and without raising the
  90 .I inexact
  91 exception.
  92 When the current rounding direction is to nearest, these
  93 functions round halfway cases to the even integer in accordance with
  94 IEEE-754.
  95 .LP
  96 The
  97 .BR rint (),
  98 .BR rintf (),
  99 and
 100 .BR rintl ()
 101 functions do the same, but will raise the
 102 .I inexact
 103 exception
 104 .RB ( FE_INEXACT ,
 105 checkable via
 106 .BR fetestexcept (3))
 107 when the result differs in value from the argument.
 108 .SH RETURN VALUE
 109 These functions return the rounded integer value.
 110
 111 If
 112 .I x
 113 is integral, +0, \-0, NaN, or infinite,
 114 .I x
 115 itself is returned.
 116 .SH ERRORS
 117 No errors occur.
 118 POSIX.1-2001 documents a range error for overflows, but see NOTES.
 119 .SH ATTRIBUTES
 120 For an explanation of the terms used in this section, see
 121 .BR attributes (7).
 122 .TS
 123 allbox;
 124 lbw26 lb lb
 125 l l l.
 126 Interface       Attribute       Value
 127 T{
 128 .BR nearbyint (),
 129 .BR nearbyintf (),
 130 .br
 131 .BR nearbyintl (),
 132 .BR rint (),
 133 .br
 134 .BR rintf (),
 135 .BR rintl ()
 136 T}      Thread safety   MT-Safe
 137 .TE
 138 .SH CONFORMING TO
 139 C99, POSIX.1-2001, POSIX.1-2008.
 140 .SH NOTES
 141 SUSv2 and POSIX.1-2001 contain text about overflow (which might set
 142 .I errno
 143 to
 144 .BR ERANGE ,
 145 or raise an
 146 .B FE_OVERFLOW
 147 exception).
 148 In practice, the result cannot overflow on any current machine,
 149 so this error-handling stuff is just nonsense.
 150 (More precisely, overflow can happen only when the maximum value
 151 of the exponent is smaller than the number of mantissa bits.
 152 For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
 153 the maximum value of the exponent is 128 (respectively, 1024),
 154 and the number of mantissa bits is 24 (respectively, 53).)
 155
 156 If you want to store the rounded value in an integer type,
 157 you probably want to use one of the functions described in
 158 .BR lrint (3)
 159 instead.
 160 .SH SEE ALSO
 161 .BR ceil (3),
 162 .BR floor (3),
 163 .BR lrint (3),
 164 .BR round (3),
 165 .BR trunc (3)