man3/floor.3

   1 .\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.
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  27 .TH FLOOR 3  2017-09-15 "" "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 .PP
  34 .BI "double floor(double " x );
  35 .BI "float floorf(float " x );
  36 .BI "long double floorl(long double " x );
  37 .fi
  38 .PP
  39 Link with \fI\-lm\fP.
  40 .PP
  41 .in -4n
  42 Feature Test Macro Requirements for glibc (see
  43 .BR feature_test_macros (7)):
  44 .in
  45 .PP
  46 .ad l
  47 .BR floorf (),
  48 .BR floorl ():
  49 .RS 4
  50 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  51     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  52     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  53 .RE
  54 .ad
  55 .SH DESCRIPTION
  56 These functions return the largest integral value that is not greater than
  57 .IR x .
  58 .PP
  59 For example,
  60 .IR floor(0.5)
  61 is 0.0, and
  62 .IR floor(\-0.5)
  63 is \-1.0.
  64 .SH RETURN VALUE
  65 These functions return the floor of
  66 .IR x .
  67 .PP
  68 If
  69 .I x
  70 is integral, +0, \-0, NaN, or an infinity,
  71 .I x
  72 itself is returned.
  73 .SH ERRORS
  74 No errors occur.
  75 POSIX.1-2001 documents a range error for overflows, but see NOTES.
  76 .SH ATTRIBUTES
  77 For an explanation of the terms used in this section, see
  78 .BR attributes (7).
  79 .TS
  80 allbox;
  81 lbw27 lb lb
  82 l l l.
  83 Interface       Attribute       Value
  84 T{
  85 .BR floor (),
  86 .BR floorf (),
  87 .BR floorl ()
  88 T}      Thread safety   MT-Safe
  89 .TE
  90 .SH CONFORMING TO
  91 C99, POSIX.1-2001, POSIX.1-2008.
  92 .PP
  93 The variant returning
  94 .I double
  95 also conforms to
  96 SVr4, 4.3BSD, C89.
  97 .SH NOTES
  98 SUSv2 and POSIX.1-2001 contain text about overflow (which might set
  99 .I errno
 100 to
 101 .BR ERANGE ,
 102 or raise an
 103 .B FE_OVERFLOW
 104 exception).
 105 In practice, the result cannot overflow on any current machine,
 106 so this error-handling stuff is just nonsense.
 107 .\" The POSIX.1-2001 APPLICATION USAGE SECTION discusses this point.
 108 (More precisely, overflow can happen only when the maximum value
 109 of the exponent is smaller than the number of mantissa bits.
 110 For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
 111 the maximum value of the exponent is 128 (respectively, 1024),
 112 and the number of mantissa bits is 24 (respectively, 53).)
 113 .SH SEE ALSO
 114 .BR ceil (3),
 115 .BR lrint (3),
 116 .BR nearbyint (3),
 117 .BR rint (3),
 118 .BR round (3),
 119 .BR trunc (3)