Hello, I have optimized the expansion of the macro whichever. In the current implementation, it generates n random values, creates O(n) functions and calls one of them. Using a sort of "inline" binary search, I was able to create an expansion which makes one call to RANDOM, O(log n) tests, and also does not create any extra function. A test with my implementation: cl-user> (macroexpand-1 '(whichever (list 1) (list 2) (list 3) (list 4) (list 5) (list 6) (list 7))) (let ((#:random-number854 (random 7))) (if (< #:random-number854 3) (if (< #:random-number854 1) (list 1) (if (< #:random-number854 2) (list 2) (list 3))) (if (< #:random-number854 5) (if (< #:random-number854 4) (list 4) (list 5)) (if (< #:random-number854 6) (list 6) (list 7))))) t Regards, Gustavo Henrique Milaré.