(%map-for-effect #'f sequences))
(let ((result (make-sequence result-type min-len)))
(multiple-value-bind (state limit from-end step endp elt setelt)
(sb!sequence:make-sequence-iterator result)
(declare (ignore limit endp elt))
(flet ((f (&rest args)
(%map-for-effect #'f sequences))
(let ((result (make-sequence result-type min-len)))
(multiple-value-bind (state limit from-end step endp elt setelt)
(sb!sequence:make-sequence-iterator result)
(declare (ignore limit endp elt))
(flet ((f (&rest args)