#!/usr/local/bin/sbcl --script (defmacro -> (form . forms) (if (null forms) form `(-> ,(nsubst form 'it (car forms)) ,@(cdr forms)))) (defun join-string (lst sep) (-> (let ((acc nil)) (dolist (str (cdr lst) (cons (car lst) (nreverse acc))) (push str acc) (push sep acc))) (apply #'concatenate 'string it))) (let ((x (list "a" "b" "c" "d"))) (print (join-string x " ")))