Entries from 2015-08-17 to 1 day
;; 2.42 (define (queens board-size) (letrec ((queen-cols (lambda (k) (if (= k 0) (list empty-board) (filter (lambda (positions) (safe? k positions)) (flatmap (lambda (rest-of-queens) (map (lambda (new-row) (adjoin-position new-row k rest-o…