I use CL/Scheme/Clojure at work. I generally prefer comprehension style ('for' in Clojure, srfi-42 in Scheme) but sometimes CL's loop let me save a few nestin

I use CL/Scheme/Clojure at work. I generally prefer comprehension style ('for' in Clojure, srfi-42 in Scheme) but sometimes CL's loop let me save a few nestings. One of such patterns is when I have to accumulate multiple kind of things while I zip through the input. Somewhat contrived example: You have a hashtable that maps integer key to a list of strings. You want to scan it just once and build two lists, strings associated with odd keys and strings associated with even keys. ;; populate input (defvar input (make-hash-table :test 'eql)) (setf (gethash 1 input) '("ichi" "hi")) (setf (gethash 2 input) '("ni" "fu")) (setf (gethash 3 input) '("san" "mi")) (setf (gethash 4 input) '("yon" "shi" "yo")) (setf (gethash 5 input) '("go" "itsu")) ;; loop (loop for k being each hash-key in input when (oddp k) append (gethash k input) into odds when (evenp k) append (gethash k input) into evens finally (return (values odds evens))) ; => ("go" "itsu" "san" "mi" "ichi" "hi") and ("yon" "shi" "yo" "ni" "fu")