_nt_alphanumeric_char (Treetop::Compiler::Metagrammar)

    # File lib/treetop/compiler/metagrammar.rb, line 2916
          def _nt_alphanumeric_char
            start_index = index
            if node_cache[:alphanumeric_char].has_key?(index)
              cached = node_cache[:alphanumeric_char][index]
              @index = cached.interval.end if cached
              return cached
            end

            i0 = index
            r1 = _nt_alpha_char
            if r1
              r0 = r1
            else
              if input.index(Regexp.new('[0-9]'), index) == index
                r2 = instantiate_node(SyntaxNode,input, index...(index + 1))
                @index += 1
              else
                r2 = nil
              end
              if r2
                r0 = r2
              else
                self.index = i0
                r0 = nil
              end
            end

            node_cache[:alphanumeric_char][start_index] = r0

            return r0
          end