Right, that’s what I said. Just because it’s efficient to implement one language that way doesn’t mean it’s efficient to do that for every language in the same

Right, that’s what I said. Just because it’s efficient to implement one language that way doesn’t mean it’s efficient to do that for every language in the same family. :) With non-variadic arithmetic functions: (defn add [x] (cons (+ (first x) (second x)) (rest (rest x)))) Your “postfix” function can remain a simple “reduce”, but can be totally agnostic of function arity. That frees you up to write the basic combinators: (defn dup [x] (cons (first x) x)) (defn zap [x] (rest x)) (defn swap [x] (cons (second x) (cons (first x) (rest (rest x))))) (defn ap [x] (apply (first x) (rest x))) ...