module Gem List = Struct.new(:value, :tail) class List def each n = self while n yield n.value n = n.tail end end def to_a ary = [] n = self while n ary.unshift n.value n = n.tail end ary end def find n = self while n v = n.value return v if yield(v) n = n.tail end nil end def prepend(value) List.new value, self end def pretty_print q # :nodoc: q.pp to_a end def self.prepend(list, value) return List.new(value) unless list List.new value, list end end end