# File lib/backports/1.9.1/stdlib/prime.rb, line 282
    def with_index(offset = 0)
      return enum_for(:with_index, offset) { Float::INFINITY } unless block_given?
      return each_with_index(&proc) if offset == 0

      each do |prime|
        yield prime, offset
        offset += 1
      end
    end