partition-group.clj

(partition-by #(mod % 3) (range 1 10))
;;((1) (2) (3) (4) (5) (6) (7) (8) (9))

(partition-by #(mod % 3) (mapcat (partial repeat 3) (range 1 10)))
;;((1 1 1) (2 2 2) (3 3 3) (4 4 4) (5 5 5) (6 6 6) (7 7 7) (8 8 8) (9 9 9))

(group-by #(mod % 3) (range 1 10))
;;{1 [1 4 7], 2 [2 5 8], 0 [3 6 9]}

(group-by #(mod % 3) (mapcat (partial repeat 3) (range 1 10)))
;;{1 [1 1 1 4 4 4 7 7 7], 2 [2 2 2 5 5 5 8 8 8], 0 [3 3 3 6 6 6 9 9 9]}