gistfile1.rb

    def reductions(*args, &fn)
      fn ||= args.shift
      Utils.verify_args(args, 0, 1)
      acc, coll = (args.empty? ? divide : [args.first, self])

      F.lazy_loop(acc, coll) do |recur, acc, coll|
        if coll.seq
          acc = fn[acc, coll.first]
          F.cons(acc, recur[acc, coll.rest])
        end
      end.conj(acc)
    end