hello.rb

# frozen_string_literal: true

class Hello
  def self.world
    'helloworld'
  end

  def self.rand_list(length, lowerb, upperb)
    0.upto(length - 1).map do
      rand(lowerb..upperb)
    end
  end

  def self.capscrumble(input)
    # combinatorial possibilities
    rr = (0..(2**input.length)).map do |i|
      bit_mask = "%0#{input.length}d" % i.to_s(2) # "1100"

      input.chars.map.with_index do |char, j|
        bit_mask[j] == '1' ? char.upcase : char.downcase
      end.join
    end[0..-2]

    puts rr.join('; ')
    rr
  end
end