# File lib/treetop/compiler/metagrammar.rb, line 2896
      def _nt_alpha_char
        start_index = index
        if node_cache[:alpha_char].has_key?(index)
          cached = node_cache[:alpha_char][index]
          @index = cached.interval.end if cached
          return cached
        end

        if input.index(Regexp.new('[A-Za-z_]'), index) == index
          r0 = instantiate_node(SyntaxNode,input, index...(index + 1))
          @index += 1
        else
          r0 = nil
        end

        node_cache[:alpha_char][start_index] = r0

        return r0
      end