Question

In researching type inference differences between F# and OCaml I found they tended to focus on nominative vs. structural type system. Then I found Distinctive traits of functional programming languages which list typing and type inference as different traits.

Since the trait article says OCaml and F# both use Damas-Milner type inference which I thought was a standard algorithm, i.e. an algorithm that does not allow for variations, how do the two traits relate? Is it that Damas-Milner is the basis upon which both type inference systems are built but that they each modify Damas-Milner based on the typing?

Also I checked the F# source code for the words Damas, Milner and Hindley and found none. A search for the word inference turned up the code for type inference.

If so, are there any papers that discuss the details of each type inference algorithm for the particular language, or do I have to look at the source code for OCaml and F#.

EDIT

Here is a page that highlights some differences related to type inference between OCaml and F#.

Answer 1

Since the trait article says OCaml and F# both use Damas-Milner type inference which I thought was a standard algorithm, i.e. an algorithm that does not allow for variations, how do the two traits relate?

The Damas-Milner algorithm (also known as Algorithm W) can be extended and, indeed, all practically-relevant implementations of it have added many extensions including both OCaml and F#.

Is it that Damas-Milner is the basis upon which both type inference systems are built but that they each modify Damas-Milner based on the typing?

Exactly, yes. In particular, OCaml has a great many different experimental extensions to a Damas-Milner core including polymorphic variants, objects, first-class modules. F# is simpler but also has some extensions that OCaml does not have, most notably overloading (primarily operators).

I don’t believe there are summary papers describing the whole type systems of either OCaml or F#. Indeed, I do not know of a paper that describes today’s F# type system. For OCaml, you have many different papers each covering different aspects. I would start with Jacques Garrigue’s own publications and then follow the references therein.