man3/fmod.3

   1 '\" t
   2 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   3 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
   4 .\"     <mtk.manpages@gmail.com>
   5 .\"
   6 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   7 .\"
   8 .\" References consulted:
   9 .\"     Linux libc source code
  10 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  11 .\"     386BSD man pages
  12 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  13 .\" Modified 2002-07-27 by Walter Harms
  14 .\"     (walter.harms@informatik.uni-oldenburg.de)
  15 .\"
  16 .TH fmod 3 (date) "Linux man-pages (unreleased)"
  17 .SH NAME
  18 fmod, fmodf, fmodl \- floating-point remainder function
  19 .SH LIBRARY
  20 Math library
  21 .RI ( libm ", " \-lm )
  22 .SH SYNOPSIS
  23 .nf
  24 .B #include <math.h>
  25 .PP
  26 .BI "double fmod(double " x ", double " y );
  27 .BI "float fmodf(float " x ", float " y );
  28 .BI "long double fmodl(long double " x ", long double " y );
  29 .fi
  30 .PP
  31 .RS -4
  32 Feature Test Macro Requirements for glibc (see
  33 .BR feature_test_macros (7)):
  34 .RE
  35 .PP
  36 .BR fmodf (),
  37 .BR fmodl ():
  38 .nf
  39     _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
  40         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  41         || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  42 .fi
  43 .SH DESCRIPTION
  44 These functions compute the floating-point remainder of dividing
  45 .I x
  46 by
  47 .IR y .
  48 The return value is
  49 .I x
  50 \-
  51 .I n
  52 *
  53 .IR y ,
  54 where
  55 .I n
  56 is the quotient of
  57 .I x
  58 /
  59 .IR y ,
  60 rounded toward zero to an integer.
  61 .SH RETURN VALUE
  62 On success, these
  63 functions return the value \fIx\fP\ \-\ \fIn\fP*\fIy\fP,
  64 for some integer
  65 .IR n ,
  66 such that the returned value has the same sign as
  67 .I x
  68 and a magnitude less than the magnitude of
  69 .IR y .
  70 .PP
  71 If
  72 .I x
  73 or
  74 .I y
  75 is a NaN, a NaN is returned.
  76 .PP
  77 If
  78 .I x
  79 is an infinity,
  80 a domain error occurs, and
  81 a NaN is returned.
  82 .PP
  83 If
  84 .I y
  85 is zero,
  86 a domain error occurs, and
  87 a NaN is returned.
  88 .PP
  89 If
  90 .I x
  91 is +0 (\-0), and
  92 .I y
  93 is not zero, +0 (\-0) is returned.
  94 .SH ERRORS
  95 See
  96 .BR math_error (7)
  97 for information on how to determine whether an error has occurred
  98 when calling these functions.
  99 .PP
 100 The following errors can occur:
 101 .TP
 102 Domain error: \fIx\fP is an infinity
 103 .I errno
 104 is set to
 105 .B EDOM
 106 (but see BUGS).
 107 An invalid floating-point exception
 108 .RB ( FE_INVALID )
 109 is raised.
 110 .TP
 111 Domain error: \fIy\fP is zero
 112 .I errno
 113 is set to
 114 .BR EDOM .
 115 An invalid floating-point exception
 116 .RB ( FE_INVALID )
 117 is raised.
 118 .\" POSIX.1 documents an optional underflow error, but AFAICT it doesn't
 119 .\" (can't?) occur -- mtk, Jul 2008
 120 .SH ATTRIBUTES
 121 For an explanation of the terms used in this section, see
 122 .BR attributes (7).
 123 .TS
 124 allbox;
 125 lbx lb lb
 126 l l l.
 127 Interface       Attribute       Value
 128 T{
 129 .na
 130 .nh
 131 .BR fmod (),
 132 .BR fmodf (),
 133 .BR fmodl ()
 134 T}      Thread safety   MT-Safe
 135 .TE
 136 .sp 1
 137 .SH STANDARDS
 138 C11, POSIX.1-2008.
 139 .SH HISTORY
 140 C99, POSIX.1-2001.
 141 .PP
 142 The variant returning
 143 .I double
 144 also conforms to
 145 SVr4, 4.3BSD, C89.
 146 .SH BUGS
 147 Before glibc 2.10, the glibc implementation did not set
 148 .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6784
 149 .I errno
 150 to
 151 .B EDOM
 152 when a domain error occurred for an infinite
 153 .IR x .
 154 .SH SEE ALSO
 155 .BR remainder (3)