| .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
| .\" |
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| .\" permission notice identical to this one. |
| .\" |
| .\" Since the Linux kernel and libraries are constantly changing, this |
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| .\" References consulted: |
| .\" Linux libc source code |
| .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) |
| .\" 386BSD man pages |
| .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) |
| .\" Modified 2002-08-10 by Walter Harms (walter.harms@informatik.uni-oldenburg.de) |
| .TH COPYSIGN 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| copysign, copysignf, copysignl \- copy sign of a number |
| .SH SYNOPSIS |
| .nf |
| .B #include <math.h> |
| .PP |
| .BI "double copysign(double " x ", double " y ); |
| .BI "float copysignf(float " x ", float " y ); |
| .BI "long double copysignl(long double " x ", long double " y ); |
| .fi |
| .PP |
| Link with \fI\-lm\fP. |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR copysign (), |
| .BR copysignf (), |
| .BR copysignl (): |
| .nf |
| _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L |
| || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
| || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE |
| .fi |
| .SH DESCRIPTION |
| These functions return a value whose absolute value matches that of |
| .IR x , |
| but whose sign bit matches that of |
| .IR y . |
| .PP |
| For example, |
| .I "copysign(42.0,\ \-1.0)" |
| and |
| .I "copysign(\-42.0, \-1.0)" |
| both return \-42.0. |
| .SH RETURN VALUE |
| On success, these functions return a value whose magnitude is taken from |
| .I x |
| and whose sign is taken from |
| .IR y . |
| .PP |
| If |
| .I x |
| is a NaN, |
| a NaN with the sign bit of |
| .I y |
| is returned. |
| .SH ERRORS |
| No errors occur. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR copysign (), |
| .BR copysignf (), |
| .BR copysignl () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| C99, POSIX.1-2001, POSIX.1-2008. |
| .\" 4.3BSD. |
| This function is defined in IEC 559 (and the appendix with |
| recommended functions in IEEE 754/IEEE 854). |
| .SH NOTES |
| On architectures where the floating-point formats are not IEEE 754 compliant, |
| these |
| functions may treat a negative zero as positive. |
| .SH SEE ALSO |
| .BR signbit (3) |