Higher-order function

higher_order_function.rb

# implemented in the controller action, result from the 
# calculator operation is passed to the Repository
 
# app/controllers/calculation.rb
def create
  h = ActiveSupport::JSON.decode(request.body)
  
  fx = lambda do |op, mod, repo|
    lambda do |x, y|
      result = mod.method(op.to_sym).to_proc[x, y]
      repo.save_calculation op, x, y, result
      result
    end
  end
 
  @result = fx[h["operation"], StatelessCalculator, Repository][h["x"], h["y"]]
  
  render :calculation_view
end