Calculating with Functions | Codewars

calculating_with_functions.rb

[:zero, :one, :two, :three, :four, :five, 
 :six, :seven, :eight, :nine].each.with_index do |method, index|
  define_method method do |function = nil|
    (function) ? function.call(index) : index
  end
end

[[:plus, :+], [:minus, :-], 
 [:times, :*], [:divided_by, :/]].each do |(method, action)|
  define_method method do |second_operand|
    ->(first_operand) { first_operand.send(action, second_operand) } 
  end
end

seven(times(five))   # => 35
four(plus(nine))     # => 13
eight(minus(three))  # => 5
six(divided_by(two)) # => 3