+(define-raw-builtin + (&rest numbers)
+ (if (null numbers)
+ "0"
+ (variable-arity numbers
+ (join numbers "+"))))
+
+(define-raw-builtin - (x &rest others)
+ (let ((args (cons x others)))
+ (variable-arity args
+ (if (null others)
+ (concat "-" (car args))
+ (join args "-")))))
+
+