Programming is not meant to be easy and it’s important to make sure that it is as cryptic as possible otherwise people other than cult members might be able to understand it. Of course, you also need to make sure it’s pure, because otherwise cult members will laughingly throw you into a pit full of spikes and the rotting remains of other heretics.
For instance, you can’t be writing this sort of thing:
(defun ss (n) (let ((s 0) (i 0)) (tagbody loop (when (> i n) (go done)) (setf s (+ s (* i i)) i (+ i 1)) (go loop) done (return-from ss s))))
This is just terrible code. Non cult members may well be able to understand it, and the cultists will have you in the pit before you know it.
You might think this was better
(defun ss (n) (loop for i from 0 to n summing (* i i)))
But in fact it’s far worse. Fellow cultists will definitely still be at the laughing and pit-throwing, and the others will certainly understand it and laugh at you because you don’t know the closed form.
Instead, you must write this:
(define (ss n) (let-values ([(a i l) (call/cc (λ (c) (values 0 0 c)))]) (l (+ a (* i i)) (+ i 1) (if (< i (- n 1)) l (λ (a i l) a)))))
This is almost a perfect solution. It’s so achingly pure and cryptic that you will be immediately appointed king of the cult and be able to do your own laughing, and throw other members into pits you have first made them dig, for which they will thank you as they slide down the spikes. Non cult members stand essentially no chance of understanding what it does and sniping about the whole silly closed-form thing: certainly the only way they will be able to learn what it does is by first joining the cult, at which point, as king, you can just throw them straight into the pit.
It’s important you understand this.