utils: Add documentation to procedures

modules/radix/utils.scm

@@ -15,6 +15,9 @@
   `(,@(map (cut cons <> association) keys) ...))
 
 (define (flat-map proc . lsts)
+  "Returns a list containg every other application of PROC to a list where the
+first element comes from the first list, the second element from the second
+list, up to the last list."
   (match lsts
     ((head-lst) (map proc head-lst))
     ((head-lst . tail-lsts)