;; The shape prelude.ml's sort-i32-by! / sort-f32-by! pair would collapse into:
;; one generic body, the comparison passed in as a function value because an
;; unconstrained type variable has no < of its own.

(defn swap! [xs [$t] i i32 j i32] ()
  (let [tmp (at xs i)]
    (set (at xs i) (at xs j))
    (set (at xs j) tmp)))

(defn sort-by! [s [$t] before? (Fn [$t $t] bool)] ()
  (let [i 1]
    (while (< i (len s))
      (let [j i]
        (while (and (> j 0) (before? (at s j) (at s (- j 1))))
          (swap! s (- j 1) j)
          (set j (- j 1))))
      (set i (+ i 1)))))

(defn main [] ()
  (let [ns [5 3 9 1]
        fs [2.5 0.5 1.5]]
    (sort-by! (slice ns 0 4) (fn [a b] (< a b)))
    (sort-by! (slice fs 0 3) (fn [a b] (> a b)))
    (dotimes [i 4] (println (at ns i)))
    (dotimes [i 3] (println (at fs i)))))