man3/floor.3

   1 .\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.
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  27 .TH FLOOR 3  2016-03-15 "" "Linux Programmer's Manual"
  28 .SH NAME
  29 floor, floorf, floorl \- largest integral value not greater than argument
  30 .SH SYNOPSIS
  31 .nf
  32 .B #include <math.h>
  33 .sp
  34 .BI "double floor(double " x );
  35 .br
  36 .BI "float floorf(float " x );
  37 .br
  38 .BI "long double floorl(long double " x );
  39 .fi
  40 .sp
  41 Link with \fI\-lm\fP.
  42 .sp
  43 .in -4n
  44 Feature Test Macro Requirements for glibc (see
  45 .BR feature_test_macros (7)):
  46 .in
  47 .sp
  48 .ad l
  49 .BR floorf (),
  50 .BR floorl ():
  51 .RS 4
  52 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  53     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  54     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  55 .RE
  56 .ad
  57 .SH DESCRIPTION
  58 These functions return the largest integral value that is not greater than
  59 .IR x .
  60
  61 For example,
  62 .IR floor(0.5)
  63 is 0.0, and
  64 .IR floor(\-0.5)
  65 is \-1.0.
  66 .SH RETURN VALUE
  67 These functions return the floor of
  68 .IR x .
  69
  70 If
  71 .I x
  72 is integral, +0, \-0, NaN, or an infinity,
  73 .I x
  74 itself is returned.
  75 .SH ERRORS
  76 No errors occur.
  77 POSIX.1-2001 documents a range error for overflows, but see NOTES.
  78 .SH ATTRIBUTES
  79 For an explanation of the terms used in this section, see
  80 .BR attributes (7).
  81 .TS
  82 allbox;
  83 lbw27 lb lb
  84 l l l.
  85 Interface       Attribute       Value
  86 T{
  87 .BR floor (),
  88 .BR floorf (),
  89 .BR floorl ()
  90 T}      Thread safety   MT-Safe
  91 .TE
  92 .SH CONFORMING TO
  93 C99, POSIX.1-2001, POSIX.1-2008.
  94
  95 The variant returning
  96 .I double
  97 also conforms to
  98 SVr4, 4.3BSD, C89.
  99 .SH NOTES
 100 SUSv2 and POSIX.1-2001 contain text about overflow (which might set
 101 .I errno
 102 to
 103 .BR ERANGE ,
 104 or raise an
 105 .B FE_OVERFLOW
 106 exception).
 107 In practice, the result cannot overflow on any current machine,
 108 so this error-handling stuff is just nonsense.
 109 .\" The POSIX.1-2001 APPLICATION USAGE SECTION discusses this point.
 110 (More precisely, overflow can happen only when the maximum value
 111 of the exponent is smaller than the number of mantissa bits.
 112 For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
 113 the maximum value of the exponent is 128 (respectively, 1024),
 114 and the number of mantissa bits is 24 (respectively, 53).)
 115 .SH SEE ALSO
 116 .BR ceil (3),
 117 .BR lrint (3),
 118 .BR nearbyint (3),
 119 .BR rint (3),
 120 .BR round (3),
 121 .BR trunc (3)