man3/rint.3

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  27 .TH RINT 3  2010-09-20 "" "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 .sp
  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 .sp
  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 .sp
  48 Link with \fI\-lm\fP.
  49 .sp
  50 .in -4n
  51 Feature Test Macro Requirements for glibc (see
  52 .BR feature_test_macros (7)):
  53 .in
  54 .sp
  55 .ad l
  56 .BR nearbyint (),
  57 .BR nearbyintf (),
  58 .BR nearbyintl ():
  59 .RS 4
  60 _XOPEN_SOURCE\ >=\ 600 || _POSIX_C_SOURCE\ >=\ 200112L || _ISOC99_SOURCE;
  61 .br
  62 or
  63 .I cc\ -std=c99
  64 .RE
  65 .br
  66 .BR rint ():
  67 .RS 4
  68 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
  69 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
  70 _POSIX_C_SOURCE\ >=\ 200112L;
  71 .br
  72 or
  73 .I cc\ -std=c99
  74 .RE
  75 .br
  76 .BR rintf (),
  77 .BR rintl ():
  78 .RS 4
  79 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
  80 _POSIX_C_SOURCE\ >=\ 200112L;
  81 .br
  82 or
  83 .I cc\ -std=c99
  84 .RE
  85 .ad b
  86 .SH DESCRIPTION
  87 The
  88 .BR nearbyint ()
  89 functions round their argument to an integer value in floating-point
  90 format, using the current rounding direction (see
  91 .BR fesetround (3))
  92 and without raising the
  93 .I inexact
  94 exception.
  95 .LP
  96 The
  97 .BR rint ()
  98 functions do the same, but will raise the
  99 .I inexact
 100 exception
 101 .RB ( FE_INEXACT ,
 102 checkable via
 103 .BR fetestexcept (3))
 104 when the result differs in value from the argument.
 105 .SH RETURN VALUE
 106 These functions return the rounded integer value.
 107
 108 If \fIx\fP is integral, +0, \-0, NaN, or infinite,
 109 \fIx\fP itself is returned.
 110 .SH ERRORS
 111 No errors occur.
 112 POSIX.1-2001 documents a range error for overflows, but see NOTES.
 113 .SH CONFORMING TO
 114 C99, POSIX.1-2001.
 115 .SH NOTES
 116 SUSv2 and POSIX.1-2001 contain text about overflow (which might set
 117 .I errno
 118 to
 119 .BR ERANGE ,
 120 or raise an
 121 .B FE_OVERFLOW
 122 exception).
 123 In practice, the result cannot overflow on any current machine,
 124 so this error-handling stuff is just nonsense.
 125 (More precisely, overflow can happen only when the maximum value
 126 of the exponent is smaller than the number of mantissa bits.
 127 For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
 128 the maximum value of the exponent is 128 (respectively, 1024),
 129 and the number of mantissa bits is 24 (respectively, 53).)
 130
 131 If you want to store the rounded value in an integer type,
 132 you probably want to use one of the functions described in
 133 .BR lrint (3)
 134 instead.
 135 .SH SEE ALSO
 136 .BR ceil (3),
 137 .BR floor (3),
 138 .BR lrint (3),
 139 .BR round (3),
 140 .BR trunc (3)