_nt_alpha_char (Treetop::Compiler::Metagrammar)

    # 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