Common Lisp can do that CL-USER> (defun non-empty-string-p (string) (and (stringp string) (plusp (length string)))) NON-EMPT

Common Lisp can do that CL-USER> (defun non-empty-string-p (string) (and (stringp string) (plusp (length string)))) NON-EMPTY-STRING-P CL-USER> (deftype non-empty-string () `(satisfies non-empty-string-p)) NON-EMPTY-STRING CL-USER> (typep "" 'non-empty-string) NIL CL-USER> (typep " " 'non-empty-string) T