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LIFO semantics

As explained in The Well-Grounded Rubyist, Fourth Edition

The LIFO principle specifies that the last item entering a collection is the first item leaving it.

LIFO means “last in, first out”: the most recently added item leaves first. A stack of plates illustrates the rule, as do printer paper and double-parked cars. section 4.1.1

Stacklike behavior can be shared across different classes through a module. An array stores the items, while pushing adds to the stack and popping removes the newest item. section 4.1.1

A stack of plates

Place plates on a stack in the order A, B, then C. Removing plates returns C first, followed by B and A. section 4.1.1

Listing 4.1 Stacklike module, encapsulating stacklike structure and behavior
module Stacklike
  def stack
    @stack ||= []         1
  end
  def add_to_stack(obj)       2
    stack.push(obj)
  end
  def take_from_stack       3
    stack.pop
  ends
end

See the Stacklike module’s push-and-pop methods and its array-backed storage. section 4.1.1

How The Well-Grounded Rubyist, Fourth Edition covers it

How deep it goes
Defines LIFO and demonstrates array-backed push and pop operations, without extending into broader stack algorithms.
Examples
Uses plates, printer paper, double-parked cars, and a Ruby Stacklike module as examples.
What you can do after
Apply it via Ruby modules by adding stacklike behavior to classes with array-backed push and pop methods.
How it connects
Connects stacks with modules, arrays, queues, and FIFO behavior.
Cover of The Well-Grounded Rubyist, Fourth Edition
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This explainer was generated by Manning's knowledge graph from the text of The Well-Grounded Rubyist, Fourth Edition. The section links point to the parts of the book it draws on.