return a string that represents increases, decreases, and stable changes in a method's length

gistfile1.rb

# :: [event] -> String -> String
def method_delta_line es, method_name
  es.select {|e| e.method_name == method_name }
    .map(&:method_length)
    .each_cons(2)
    .map {|c,n| ["^","v","-"][(c <=> n) + 1] }
    .join
end