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|
(* TEST
expect;
*)
type _ constant =
| Int: int -> int constant
| Bool: bool -> bool constant
type (_, _, _) binop =
| Eq: ('a, 'a, bool) binop
| Leq: ('a, 'a, bool) binop
| Add: (int, int, int) binop
let eval (type a) (type b) (type c) (bop:(a,b,c) binop) (x:a constant)
(y:b constant) : c constant =
match bop, x, y with
| Eq, Bool x, Bool y -> Bool (if x then y else not y)
| Leq, Int x, Int y -> Bool (x <= y)
| Leq, Bool x, Bool y -> Bool (x <= y)
| Add, Int x, Int y -> Int (x + y)
let _ = eval Eq (Int 2) (Int 3)
[%%expect{|
type _ constant = Int : int -> int constant | Bool : bool -> bool constant
type (_, _, _) binop =
Eq : ('a, 'a, bool) binop
| Leq : ('a, 'a, bool) binop
| Add : (int, int, int) binop
Lines 12-16, characters 2-36:
12 | ..match bop, x, y with
13 | | Eq, Bool x, Bool y -> Bool (if x then y else not y)
14 | | Leq, Int x, Int y -> Bool (x <= y)
15 | | Leq, Bool x, Bool y -> Bool (x <= y)
16 | | Add, Int x, Int y -> Int (x + y)
Warning 8 [partial-match]: this pattern-matching is not exhaustive.
Here is an example of a case that is not matched:
(Eq, Int _, _)
val eval : ('a, 'b, 'c) binop -> 'a constant -> 'b constant -> 'c constant =
<fun>
Exception: Match_failure ("", 12, 2).
|}];;
|
