dup - Duplicate the object which is on top of the stack
any dup -> any any
2 dup -> 2 2
(hello) dup -> (hello) (hello)
Raises StackUnderflow error if the stack is empty.
docu edited by Sirko Straube
/builddir/build/BUILD/nest-simulator-3.3/nest-simulator-3.3/sli/slistack.cc