class RubyCritic::Rating

def self.from_cost(cost)
  if    cost <= 2  then new('A')
  elsif cost <= 4  then new('B')
  elsif cost <= 8  then new('C')
  elsif cost <= 16 then new('D')
  else
    new('F')
  end
end

def initialize(letter)
  @letter = letter
end

def to_h
  @letter
end

def to_json(*options)
  to_h.to_json(*options)
end

def to_s
  @letter
end