"i had to write very similar code (deleting from a linked list) a couple of days ago. i wasn't the easiest code to write, and i needed several iterations before

"i had to write very similar code (deleting from a linked list) a couple of days ago. i wasn't the easiest code to write, and i needed several iterations before my tests were ok, but i remember feeling happy that the final result was clear and correct." How was this not easy code to write? I imagine it would have looked like this, but in your language of choice: (defun remove-if (lst pred) (if (null lst) nil (if (funcall pred (first lst)) (remove-if (rest lst) pred) (cons (first lst) (remove-if (rest lst) pred)) ) ) ) This is straightforward and basically follows from the definition of a list: either null (empty) or a pair whose second element is a list. The C version is uglier because of the need to deallocate removed nodes, track pointers, etc., but it still follows from the definition of a list.