man3/fmod.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
   3 .\"     <mtk.manpages@gmail.com>
   4 .\"
   5 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   6 .\"
   7 .\" References consulted:
   8 .\"     Linux libc source code
   9 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  10 .\"     386BSD man pages
  11 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  12 .\" Modified 2002-07-27 by Walter Harms
  13 .\"     (walter.harms@informatik.uni-oldenburg.de)
  14 .\"
  15 .TH FMOD 3  2021-03-22 "" "Linux Programmer's Manual"
  16 .SH NAME
  17 fmod, fmodf, fmodl \- floating-point remainder function
  18 .SH LIBRARY
  19 Math library
  20 .RI ( libm ", " \-lm )
  21 .SH SYNOPSIS
  22 .nf
  23 .B #include <math.h>
  24 .PP
  25 .BI "double fmod(double " x ", double " y );
  26 .BI "float fmodf(float " x ", float " y );
  27 .BI "long double fmodl(long double " x ", long double " y );
  28 .fi
  29 .PP
  30 .RS -4
  31 Feature Test Macro Requirements for glibc (see
  32 .BR feature_test_macros (7)):
  33 .RE
  34 .PP
  35 .BR fmodf (),
  36 .BR fmodl ():
  37 .nf
  38     _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
  39         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  40         || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  41 .fi
  42 .SH DESCRIPTION
  43 These functions compute the floating-point remainder of dividing
  44 .I x
  45 by
  46 .IR y .
  47 The return value is
  48 .IR x
  49 \-
  50 .I n
  51 *
  52 .IR y ,
  53 where
  54 .I n
  55 is the quotient of
  56 .I x
  57 /
  58 .IR y ,
  59 rounded toward zero to an integer.
  60 .SH RETURN VALUE
  61 On success, these
  62 functions return the value \fIx\fP\ \-\ \fIn\fP*\fIy\fP,
  63 for some integer
  64 .IR n ,
  65 such that the returned value has the same sign as
  66 .I x
  67 and a magnitude less than the magnitude of
  68 .IR y .
  69 .PP
  70 If
  71 .I x
  72 or
  73 .I y
  74 is a NaN, a NaN is returned.
  75 .PP
  76 If
  77 .I x
  78 is an infinity,
  79 a domain error occurs, and
  80 a NaN is returned.
  81 .PP
  82 If
  83 .I y
  84 is zero,
  85 a domain error occurs, and
  86 a NaN is returned.
  87 .PP
  88 If
  89 .I x
  90 is +0 (\-0), and
  91 .I y
  92 is not zero, +0 (\-0) is returned.
  93 .SH ERRORS
  94 See
  95 .BR math_error (7)
  96 for information on how to determine whether an error has occurred
  97 when calling these functions.
  98 .PP
  99 The following errors can occur:
 100 .TP
 101 Domain error: \fIx\fP is an infinity
 102 .I errno
 103 is set to
 104 .BR EDOM
 105 (but see BUGS).
 106 An invalid floating-point exception
 107 .RB ( FE_INVALID )
 108 is raised.
 109 .TP
 110 Domain error: \fIy\fP is zero
 111 .I errno
 112 is set to
 113 .BR EDOM .
 114 An invalid floating-point exception
 115 .RB ( FE_INVALID )
 116 is raised.
 117 .\" POSIX.1 documents an optional underflow error, but AFAICT it doesn't
 118 .\" (can't?) occur -- mtk, Jul 2008
 119 .SH ATTRIBUTES
 120 For an explanation of the terms used in this section, see
 121 .BR attributes (7).
 122 .ad l
 123 .nh
 124 .TS
 125 allbox;
 126 lbx lb lb
 127 l l l.
 128 Interface       Attribute       Value
 129 T{
 130 .BR fmod (),
 131 .BR fmodf (),
 132 .BR fmodl ()
 133 T}      Thread safety   MT-Safe
 134 .TE
 135 .hy
 136 .ad
 137 .sp 1
 138 .SH CONFORMING TO
 139 C99, POSIX.1-2001, POSIX.1-2008.
 140 .PP
 141 The variant returning
 142 .I double
 143 also conforms to
 144 SVr4, 4.3BSD, C89.
 145 .SH BUGS
 146 Before version 2.10, the glibc implementation did not set
 147 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6784
 148 .I errno
 149 to
 150 .B EDOM
 151 when a domain error occurred for an infinite
 152 .IR x .
 153 .SH SEE ALSO
 154 .BR remainder (3)