# File lib/treetop/compiler/metagrammar.rb, line 2437
      def _nt_prefix
        start_index = index
        if node_cache[:prefix].has_key?(index)
          cached = node_cache[:prefix][index]
          if cached
            node_cache[:prefix][index] = cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
            @index = cached.interval.end
          end
          return cached
        end

        i0 = index
        if (match_len = has_terminal?('&', false, index))
          r1 = instantiate_node(AndPredicate,input, index...(index + match_len))
          @index += match_len
        else
          terminal_parse_failure('\'&\'')
          r1 = nil
        end
        if r1
          r1 = SyntaxNode.new(input, (index-1)...index) if r1 == true
          r0 = r1
        else
          if (match_len = has_terminal?('!', false, index))
            r2 = instantiate_node(NotPredicate,input, index...(index + match_len))
            @index += match_len
          else
            terminal_parse_failure('\'!\'')
            r2 = nil
          end
          if r2
            r2 = SyntaxNode.new(input, (index-1)...index) if r2 == true
            r0 = r2
          else
            if (match_len = has_terminal?('~', false, index))
              r3 = instantiate_node(TransientPrefix,input, index...(index + match_len))
              @index += match_len
            else
              terminal_parse_failure('\'~\'')
              r3 = nil
            end
            if r3
              r3 = SyntaxNode.new(input, (index-1)...index) if r3 == true
              r0 = r3
            else
              @index = i0
              r0 = nil
            end
          end
        end

        node_cache[:prefix][start_index] = r0

        r0
      end