final protected function _matrix($i, $j, $k = null, $s = null, $d = null) {return
		dfa(dfa(dfc($this, function($k, $s) {return
			$this->json($k, $s)
		;}, [$k ?: df_caller_f(), df_scope_code($this->scope($s))]), $i, []), $j, $d)
	;}