47 lines
1.8 KiB
OCaml
47 lines
1.8 KiB
OCaml
(** Infer the type of a given term and, if exists, returns the type of the term *)
|
|
let typeof t =
|
|
let rec infer env = function
|
|
| Term.Var id ->
|
|
( (match TypeSubstitution.find id env with
|
|
| Some ty -> Some ty
|
|
| None -> Some (Type.Var id))
|
|
, env )
|
|
| Term.IntConst _ -> Some Type.Int, env
|
|
| Term.Binop (t1, _, t2) ->
|
|
(* Both operands must have type Int *)
|
|
(match infer env t1, infer env t2 with
|
|
| (Some ty1, _), (Some ty2, _) ->
|
|
(match Unification.unify ty1 Type.Int, Unification.unify ty2 Type.Int with
|
|
| Some env1, Some env2 -> Some Type.Int, TypeSubstitution.compose env1 env2
|
|
| _ -> None, env)
|
|
| _, _ -> None, env)
|
|
| Term.Pair (t1, t2) ->
|
|
(match infer env t1, infer env t2 with
|
|
| (Some ty1, _), (Some ty2, _) -> Some (Type.Product (ty1, ty2)), env
|
|
| _, _ -> None, env)
|
|
| Term.Proj (proj, t) ->
|
|
(* Check if the term is a pair *)
|
|
(match infer env t with
|
|
| Some (Type.Product (ty1, ty2)), _ ->
|
|
(match proj with
|
|
| Term.First -> Some ty1, env
|
|
| Term.Second -> Some ty2, env)
|
|
| _ -> None, env)
|
|
| Term.Fun (id, body) ->
|
|
(match infer env body with
|
|
| Some ty_body, env' ->
|
|
(match infer env' (Term.Var id) with
|
|
| Some ty, _ -> Some (Type.Arrow (ty, ty_body)), env'
|
|
| None, _ -> Some (Type.Arrow (Type.Var id, ty_body)), env')
|
|
| _ -> None, env)
|
|
| Term.App (t1, t2) ->
|
|
(* Check if the function type matches the arguments *)
|
|
(match infer env t1, infer env t2 with
|
|
| (Some (Type.Arrow (ty_param, ty_fn)), _), (Some ty_args, _) ->
|
|
(match Unification.unify ty_param ty_args with
|
|
| Some _ -> Some ty_fn, env
|
|
| None -> None, env)
|
|
| _, _ -> None, env)
|
|
in
|
|
fst (infer TypeSubstitution.empty t)
|
|
;;
|