_nt_prefix (Treetop::Compiler::Metagrammar)

    # File lib/treetop/compiler/metagrammar.rb, line 1733
          def _nt_prefix
            start_index = index
            if node_cache[:prefix].has_key?(index)
              cached = node_cache[:prefix][index]
              @index = cached.interval.end if cached
              return cached
            end

            i0 = index
            if input.index('&', index) == index
              r1 = instantiate_node(AndPredicate,input, index...(index + 1))
              @index += 1
            else
              terminal_parse_failure('&')
              r1 = nil
            end
            if r1
              r0 = r1
            else
              if input.index('!', index) == index
                r2 = instantiate_node(NotPredicate,input, index...(index + 1))
                @index += 1
              else
                terminal_parse_failure('!')
                r2 = nil
              end
              if r2
                r0 = r2
              else
                if input.index('~', index) == index
                  r3 = instantiate_node(TransientPrefix,input, index...(index + 1))
                  @index += 1
                else
                  terminal_parse_failure('~')
                  r3 = nil
                end
                if r3
                  r0 = r3
                else
                  self.index = i0
                  r0 = nil
                end
              end
            end

            node_cache[:prefix][start_index] = r0

            return r0
          end