stack.go
func NewStack(entries ...interface{}) *Stack {
	retval := &Stack{}
	retval.underlyer = NewLinkedList()

	for _, entry := range entries {
		retval.Push(entry)
	}
	return retval
}
func NewStack(entries ...interface{}) *Stack {
	retval := &Stack{}
	retval.underlyer = NewLinkedList()

	for _, entry := range entries {
		retval.Push(entry)
	}
	return retval
}
// NewStack instantiates a new FILO structure.