The copy command creates a copy of its argument, which is
typically a list of some type. If B is a list and A
:= B, then A and B point to the same list, and so
changing one will change the other. But if A := copy(B),
then A and B will point to different lists with the
same values, and so can be changed individually.
Input:
Output:
Output:
Input:
Input:
Output: