Taking out second element from Stack

I am learning Scala. Ho开发者_JS百科wever, on the exercise, I have some problem with Stack. How can I remove the second element from stack. I have to remove second element and put back the top element.

Thanks your advance

i dont know scala but normally you would do

variable = pop()
pop()
push(variable) 

save the first element, pop the second one to nirvana and then push the first element on top again

I know nothing about Scala, but a stack is a stack.

Call popon the stack and assign the returned value to a temporary variable, then pop again and push back the element you assigned with the first call tot pop.

Pseudo code:

tempVar = stack.pop();
stack.pop();
stack.push(tempVar);

Not much difference between a Stack and a List, and the Scala API documentation says this as well.

If using a List, a different approach to this is:

val result: (Option[T], List[T]) = myList match {
  case first :: x :: rest => (Some(x), first :: rest)
  case list => (None, list)
}

The explicit type on the result is for clarity. The advantage to this is you wont throw an exception if there is no second item, and it is a decent example of how to use pattern matching.