man3/rint.3

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  23 .TH RINT 3  2007-07-26 "" "Linux Programmer's Manual"
  24 .SH NAME
  25 nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl \- round to nearest integer
  26 .SH SYNOPSIS
  27 .nf
  28 .B #include <math.h>
  29 .sp
  30 .BI "double nearbyint(double " x );
  31 .br
  32 .BI "float nearbyintf(float " x );
  33 .br
  34 .BI "long double nearbyintl(long double " x );
  35 .sp
  36 .BI "double rint(double " x );
  37 .br
  38 .BI "float rintf(float " x );
  39 .br
  40 .BI "long double rintl(long double " x );
  41 .fi
  42 .sp
  43 Link with \fI\-lm\fP.
  44 .sp
  45 .in -4n
  46 Feature Test Macro Requirements for glibc (see
  47 .BR feature_test_macros (7)):
  48 .in
  49 .sp
  50 .ad l
  51 .BR nearbyint (),
  52 .BR nearbyintf (),
  53 .BR nearbyintl ():
  54 _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
  55 .I cc\ -std=c99
  56 .br
  57 .BR rint (),
  58 .BR rintf (),
  59 .BR rintl ():
  60 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
  61 .I cc\ -std=c99
  62 .ad b
  63 .SH DESCRIPTION
  64 The
  65 .BR nearbyint ()
  66 functions round their argument to an integer value in floating point
  67 format, using the current rounding direction and without raising the
  68 .I inexact
  69 exception.
  70 .LP
  71 The
  72 .BR rint ()
  73 functions do the same, but will raise the
  74 .I inexact
  75 exception when the result differs in value from the argument.
  76 .SH "RETURN VALUE"
  77 The rounded integer value.
  78 If \fIx\fP is integral or infinite,
  79 \fIx\fP itself is returned.
  80 .SH ERRORS
  81 No errors other than
  82 .B EDOM
  83 and
  84 .B ERANGE
  85 can occur.
  86 If \fIx\fP is NaN, then NaN is returned and
  87 .I errno
  88 may be set to
  89 .BR EDOM .
  90 .SH "CONFORMING TO"
  91 C99.
  92 .SH NOTES
  93 SUSv2 and POSIX.1-2001 contain text about overflow (which might set
  94 .I errno
  95 to
  96 .BR ERANGE ,
  97 or raise an exception).
  98 In practice, the result cannot overflow on any current machine,
  99 so this error-handling stuff is just nonsense.
 100 (More precisely, overflow can happen only when the maximum value
 101 of the exponent is smaller than the number of mantissa bits.
 102 For the IEEE-754 standard 32-bit and 64-bit floating point numbers
 103 the maximum value of the exponent is 128 (respectively, 1024), and the number
 104 of mantissa bits is 24 (respectively, 53).)
 105 .SH "SEE ALSO"
 106 .BR ceil (3),
 107 .BR floor (3),
 108 .BR lrint (3),
 109 .BR round (3),
 110 .BR trunc (3)