Stack - scala implementation / performance issue

Question

I looked at scala-lang notes on various data structures and their performance characteristics.

I noticed that it immutable.Stackhas C (Const.) Complexity for both adding and adding, while the stack mutable.Stackhas C complexity for adding and L (linear) complexity for adding. It surprised me a little.

I believe that “adding” simply means push()to the top of the stack. And since the difficulties for adding and adding are different, does this mean that the “add” actually puts something at the bottom of the stack? Why does it work better (C for mutable) than adding (L for mutable)? And also, how can I even report to the stack? I do not see any method suitable for this in scaladoc .

EDIT.

As @ Łukasz noted in the comments, you can add and add to the stack with +:and operators :+. The question remains, though - why is adding working better (faster) than adding to the stack? Should I add from below and not push up?

Answer 1

, , . , push Stack , :+ , :+ SeqLike, ,

List ::, . List L, Stack

:

def push[B >: A](elem: B): Stack[B] = new Stack(elem :: elems)

mutable :

def push(elem: A): this.type = { elems = elem :: elems; this }

, Stack 2.11

P.S. 2.12, , , 2.11

P.P.S. Stack, , , , Stack , , L append column