COPYSIGN
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
Page Index
NAME
copysign, copysignf, copysignl - copy sign of a number
SYNOPSIS
#include <math.h>
double copysign(double x, double y);
float copysignf(float x, float y);
long double copysignl(long double x, long double y);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
copysign(),
copysignf(),
copysignl():
-
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
These functions return a value whose absolute value matches that of
x,
but whose sign bit matches that of
y.
For example,
copysign(42.0, -1.0)
and
copysign(-42.0, -1.0)
both return -42.0.
RETURN VALUE
On success, these functions return a value whose magnitude is taken from
x
and whose sign is taken from
y.
If
x
is a NaN,
a NaN with the sign bit of
y
is returned.
ERRORS
No errors occur.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
copysign(),
copysignf(),
copysignl()
| Thread safety | MT-Safe
|
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
This function is defined in IEC 559 (and the appendix with
recommended functions in IEEE 754/IEEE 854).
NOTES
On architectures where the floating-point formats are not IEEE 754 compliant,
these
functions may treat a negative zero as positive.
SEE ALSO
signbit(3)
COLOPHON
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