Tuple type (hm-con "*" TYPES); list type (hm-con "list" (TYPE)).
ocaml-infer-tuple threads substitution through each item left-to-right.
ocaml-infer-list unifies all items with a fresh 'a (giving 'a list for
empty []).
Pretty-printer renders 'Int * Int' for tuples and 'Int list' for lists,
matching standard OCaml notation.
Examples:
fun x y -> (x, y) : 'a -> 'b -> 'a * 'b
fun x -> [x; x] : 'a -> 'a list
[] : 'a list
OCaml-on-SX is the deferred second consumer for lib/guest/hm.sx step 8.
lib/ocaml/infer.sx assembles Algorithm W on top of the shipped algebra:
- Var: lookup + hm-instantiate.
- Fun: fresh-tv per param, auto-curried via recursion.
- App: unify against hm-arrow, fresh-tv for result.
- Let: generalize rhs over (ftv(t) - ftv(env)) — let-polymorphism.
- If: unify cond with Bool, both branches with each other.
- Op (+, =, <, etc.): builtin signatures (int*int->int monomorphic,
=/<> polymorphic 'a->'a->bool).
Tests pass for: literals, fun x -> x : 'a -> 'a, let id ... id 5/id true,
fun f x -> f (f x) : ('a -> 'a) -> 'a -> 'a (twice).
Pending: tuples, lists, pattern matching, let-rec, modules in HM.
