;;;; A generic conversion from an enum, licensed by {:where (is-enum $t)}. is-enum
;;;; admits exactly the enums and entails is-ordered and is-equal, so a body under
;;;; it may convert, compare and test for equality, at any enum.

(defenum Color [red green blue])
(defenum Size [small 10  large 20])

(defn code [x $t] i32
  {:where (is-enum $t)}
  (i32 x))

(defn is-later [a $t b $t] bool
  {:where (is-enum $t)}
  (> a b))

(defn is-same [a $t b $t] bool
  {:where (is-enum $t)}
  (and (= a b) (<= a b)))

(defn main [] i32
  (let [c (Color 2)
        s (Size 20)]
    (println (code c))                           ; 2
    (println (code s))                           ; 20
    (println (is-later c (Color 0)))               ; true
    (println (is-same (Color 1) (Color 1)))        ; true
    (println (f64 (code s))))                    ; 20
  0)