2018-fumichan-thesis / sinatra-practice / form-sample / vendor / bundle / ruby / 2.5.0 / gems / backports-3.11.4 / lib / backports / 2.4.0 / enumerable / sum.rb

module Enumerable
  def sum(accumulator = 0, &block)
    values = block_given? ? map(&block) : self
    values.inject(accumulator, :+)
  end unless method_defined? :sum
end