man3/copysign.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .\" References consulted:
   6 .\"     Linux libc source code
   7 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
   8 .\"     386BSD man pages
   9 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  10 .\" Modified 2002-08-10 by Walter Harms (walter.harms@informatik.uni-oldenburg.de)
  11 .TH COPYSIGN 3  2021-03-22 "Linux man-pages (unreleased)" "Linux Programmer's Manual"
  12 .SH NAME
  13 copysign, copysignf, copysignl \- copy sign of a number
  14 .SH LIBRARY
  15 Math library
  16 .RI ( libm ", " \-lm )
  17 .SH SYNOPSIS
  18 .nf
  19 .B #include <math.h>
  20 .PP
  21 .BI "double copysign(double " x ", double " y );
  22 .BI "float copysignf(float " x ", float " y );
  23 .BI "long double copysignl(long double " x ", long double " y );
  24 .fi
  25 .PP
  26 .RS -4
  27 Feature Test Macro Requirements for glibc (see
  28 .BR feature_test_macros (7)):
  29 .RE
  30 .PP
  31 .BR copysign (),
  32 .BR copysignf (),
  33 .BR copysignl ():
  34 .nf
  35     _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
  36         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  37         || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  38 .fi
  39 .SH DESCRIPTION
  40 These functions return a value whose absolute value matches that of
  41 .IR x ,
  42 but whose sign bit matches that of
  43 .IR y .
  44 .PP
  45 For example,
  46 .I "copysign(42.0,\ \-1.0)"
  47 and
  48 .I "copysign(\-42.0, \-1.0)"
  49 both return \-42.0.
  50 .SH RETURN VALUE
  51 On success, these functions return a value whose magnitude is taken from
  52 .I x
  53 and whose sign is taken from
  54 .IR y .
  55 .PP
  56 If
  57 .I x
  58 is a NaN,
  59 a NaN with the sign bit of
  60 .I y
  61 is returned.
  62 .SH ERRORS
  63 No errors occur.
  64 .SH ATTRIBUTES
  65 For an explanation of the terms used in this section, see
  66 .BR attributes (7).
  67 .ad l
  68 .nh
  69 .TS
  70 allbox;
  71 lbx lb lb
  72 l l l.
  73 Interface       Attribute       Value
  74 T{
  75 .BR copysign (),
  76 .BR copysignf (),
  77 .BR copysignl ()
  78 T}      Thread safety   MT-Safe
  79 .TE
  80 .hy
  81 .ad
  82 .sp 1
  83 .SH STANDARDS
  84 C99, POSIX.1-2001, POSIX.1-2008.
  85 .\" 4.3BSD.
  86 This function is defined in IEC 559 (and the appendix with
  87 recommended functions in IEEE 754/IEEE 854).
  88 .SH NOTES
  89 On architectures where the floating-point formats are not IEEE 754 compliant,
  90 these
  91 functions may treat a negative zero as positive.
  92 .SH SEE ALSO
  93 .BR signbit (3)