A Common-Sense Guide to Data Structures and Algorithms, Second Edition, 2nd Edition

Abstract Data Types

Most programming languages don’t actually come with the stack as a built-in data type or class. Instead, it’s up to you to implement it yourself. This is a stark contrast with arrays, which are available in most languages.

To create a stack, then, you generally have to use one of the built-in data structures to actually hold the data. Here is one way to implement a stack using Ruby, which uses an array under the hood:

class Stack
  def initialize
    @data = []
  end

  def push(element)
    @data << element
  end

  def pop
    @data.pop
  end

  def read
    @data.last
  end
end

As you can see, our stack implementation stores the data in an array called @data.

Whenever a stack is initiated, ...