class Vertex attr_accessor :id, :edges def initialize(id, edges=[]) @id = id @edges = edges end def print puts "#{ @id }" @edges.each do |edge| puts edge end end end class Edge attr_accessor :id, :from, :to, :length def initialize(id, from…

戻り値 p system "ls" # => true p `ls` # => "Capfile\nGemfile\nGemfile.lock\n...." エラー時の挙動 p system "ls2" # => nil p `ls2` # => No such file or directory - ls2 (Errno::ENOENT) の例外が発生し、 空文字列がかえる p ls2 の例については be…