1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
3 .\" %%%LICENSE_START(VERBATIM)
4 .\" Permission is granted to make and distribute verbatim copies of this
5 .\" manual provided the copyright notice and this permission notice are
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8 .\" Permission is granted to copy and distribute modified versions of this
9 .\" manual under the conditions for verbatim copying, provided that the
10 .\" entire resulting derived work is distributed under the terms of a
11 .\" permission notice identical to this one.
13 .\" Since the Linux kernel and libraries are constantly changing, this
14 .\" manual page may be incorrect or out-of-date. The author(s) assume no
15 .\" responsibility for errors or omissions, or for damages resulting from
16 .\" the use of the information contained herein. The author(s) may not
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18 .\" which is licensed free of charge, as they might when working
21 .\" Formatted or processed versions of this manual, if unaccompanied by
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25 .\" References consulted:
26 .\" Linux libc source code
27 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
29 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
30 .\" Modified 2002-08-10 by Walter Harms (walter.harms@informatik.uni-oldenburg.de)
31 .TH COPYSIGN 3 2017-09-15 "GNU" "Linux Programmer's Manual"
33 copysign, copysignf, copysignl \- copy sign of a number
38 .BI "double copysign(double " x ", double " y );
39 .BI "float copysignf(float " x ", float " y );
40 .BI "long double copysignl(long double " x ", long double " y );
46 Feature Test Macro Requirements for glibc (see
47 .BR feature_test_macros (7)):
55 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
56 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
57 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
61 These functions return a value whose absolute value matches that of
63 but whose sign bit matches that of
67 .I "copysign(42.0,\ \-1.0)"
69 .I "copysign(\-42.0, \-1.0)"
72 On success, these functions return a value whose magnitude is taken from
74 and whose sign is taken from
80 a NaN with the sign bit of
86 For an explanation of the terms used in this section, see
92 Interface Attribute Value
97 T} Thread safety MT-Safe
100 C99, POSIX.1-2001, POSIX.1-2008.
102 This function is defined in IEC 559 (and the appendix with
103 recommended functions in IEEE 754/IEEE 854).
105 On architectures where the floating-point formats are not IEEE 754 compliant,
107 functions may treat a negative zero as positive.