# File lib/treetop/compiler/metagrammar.rb, line 4039
      def _nt_alphanumeric_char
        start_index = index
        if node_cache[:alphanumeric_char].has_key?(index)
          cached = node_cache[:alphanumeric_char][index]
          if cached
            node_cache[:alphanumeric_char][index] = cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
            @index = cached.interval.end
          end
          return cached
        end

        i0 = index
        r1 = _nt_alpha_char
        if r1
          r1 = SyntaxNode.new(input, (index-1)...index) if r1 == true
          r0 = r1
        else
          if has_terminal?(@regexps[gr = '\A[0-9]'] ||= Regexp.new(gr), :regexp, index)
            r2 = true
            @index += 1
          else
            terminal_parse_failure('[0-9]')
            r2 = nil
          end
          if r2
            r2 = SyntaxNode.new(input, (index-1)...index) if r2 == true
            r0 = r2
          else
            @index = i0
            r0 = nil
          end
        end

        node_cache[:alphanumeric_char][start_index] = r0

        r0
      end