# File lib/treetop/compiler/metagrammar.rb, line 1733
      def _nt_prefix
        start_index = index
        if node_cache[:prefix].has_key?(index)
          cached = node_cache[:prefix][index]
          @index = cached.interval.end if cached
          return cached
        end

        i0 = index
        if input.index('&', index) == index
          r1 = instantiate_node(AndPredicate,input, index...(index + 1))
          @index += 1
        else
          terminal_parse_failure('&')
          r1 = nil
        end
        if r1
          r0 = r1
        else
          if input.index('!', index) == index
            r2 = instantiate_node(NotPredicate,input, index...(index + 1))
            @index += 1
          else
            terminal_parse_failure('!')
            r2 = nil
          end
          if r2
            r0 = r2
          else
            if input.index('~', index) == index
              r3 = instantiate_node(TransientPrefix,input, index...(index + 1))
              @index += 1
            else
              terminal_parse_failure('~')
              r3 = nil
            end
            if r3
              r0 = r3
            else
              self.index = i0
              r0 = nil
            end
          end
        end

        node_cache[:prefix][start_index] = r0

        return r0
      end