The CopySign(x, y) function returns x with its sign changed to that of y. No multiplication is performed on x if its sign is changed in the result.

If x is real, abs(x) = CopySign(x,1) and the sign of x can be obtained by using CopySign(1,x).

If x is undefined, CopySign(x,y) returns x and no event is signaled.

If y is real, CopySign maps onto complex numerics. If y is unordered with 0 but it is not a real undefined, an invalid_operation event is signaled.

If y is a real undefined (i.e., y is undefined or Float(undefined)), CopySign(x,y) returns y*x and no event is signaled (unless a prior rule applies).

If symbolic data is used in the calling sequence, this function returns unevaluated.

The CopySign command is thread-safe as of Maple 15.

For more information on thread safety, see index/threadsafe.