As a fun exercise, Morgan and I are implement shift, unshift, push and pop in ruby and js. The return is nbd. The changing the array in place stumped me. Bc I didn’t realize you change self.

exercise.rb

class Array

  def shift
    output  = self.first
    self = self[1..-1]
    output
  end

  def unshift(item)
    [item] + self
  end

  def push(item)
    self << item
  end

  def pop
    self.last
  end
end

arr = %w(a b c d e)
puts arr.shift.inspect
puts arr.inspect

exercise.rb:5: Can't change the value of self
    self = self[1..-1]