double copysign(double x, doubley);
float copysignf(floatx, floaty);
long double copysignl(long doublex, long doubley);
These functions shall produce a value with the magnitude of x
and the sign of y. On implementations that represent
a signed zero but do not treat negative zero consistently in arithmetic
operations, these functions regard the sign of zero as
Upon successful completion, these functions shall return a value with
the magnitude of x and the sign of y.
No errors are defined.
The following sections are informative.
signbit() , the Base Definitions volume of IEEE Std 1003.1-2001,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at