10/03/13 23:27:40
後者
irb1.9> class C; include Enumerable; def initialize; @a=[1,2,3]; end; def each(&b); @a.each(&b); end; end
irb1.9> p C.new.each
#<Enumerator:0x931483c>
irb1.9> class C; include Enumerable; def initialize; @a=[1,2,3]; end; def each; @a.each{|e| yield(e)}; end; end
irb1.9> C.new.each
LocalJumpError: no block given (yield)