Plaster

common-lisp
(defun g!-symbol-p (s) (and (symbolp s) (> (length (symbol-name s)) 2) (string= (symbol-name s) "G!" :start1 0 :end1 2))) (defun flatten (x) (labels ((rec (x acc) (cond ((null x) acc) ((atom x) (cons x acc)) (t (rec (car x) (rec (cdr x) acc)))))) (rec x nil))) (defmacro defmacro/g! (name args &rest body) (let ((syms (remove-duplicates (remove-if-not #'g!-symbol-p (flatten body))))) `(defmacro ,name ,args (let ,(mapcar (lambda (s) `(,s (gensym ,(subseq (symbol-name s) 2)))) syms) ,@body)))) (defmacro/g! nif2 (expr pos zero neg) `(let ((,g!result ,expr)) (cond ((plusp ,g!result) ,pos) ((zerop ,g!result ,zero)) (t ,neg))))