Hi Bob,

I have been teaching OCaml for a while, and like you I found error
messages to be a major issue. This motivated my recent work on
improving type error messages for OCaml.

My patch is ready for action.

opam switch 4.03.0+pr102
ocamlc -new-type-errors -strict-sequence test.ml

For more information: http://arthur.chargueraud.org/teach/ocaml/

If you have a chance to try it on beginners, please share your feedback!

Best,
Arthur Charguéraud


PS: I know of on-going efforts to try and improve parsing errors too
---it be great to have those fixed too.

PPS: although my patch is usable, I have planned to fix a few things.
- Have a two-column display for type errors on applications,
     with expected types and provided types.
- Remove bracket delimiters around types and use newlines instead.
- Have "-new-type-errors" imply "-strict-sequence",
- Document the fact it does not support GADTs, and does not
    typecheck with "-principal", in particular code that uses overloading
    of record fields.
- Isolate the code associated with "-new-type-errors" so that the patch
    may have a chance of being considered for integration in OCaml.


>
> Greetings. Bob Muller here, in the CS dept. at Boston College. I've set out to
> develop an intro CS course in ML that I hope will be well-suited for similar
> universities in the US. My original plan was to teach the course in SML but
> after talking with a few people at neighboring schools, I switched to OCaml. I
> am now in the final weeks of the first run of the course.  I plan to document
> my experience more fully at some point but I wanted to touch base with the
> OCaml community because I'm teaching the course again in the spring and I am
> leaning toward switching to F#.
>
> While OCaml has in many respects been great and it's easy to see that my
> students find the OCaml style of coding very compelling, there are significant
> problems. Of course, OCaml wasn't designed for teaching but I'm hoping that
> someone on this list might be able to advise me about solutions to some of
> these that I just don't know about.
>
> 1. Error messages: It's difficult to give good type errors for ML but I was
> hoping that the state-of-the-art of type error reporting had improved. When my
> students receive a type error, they are utterly mystified,
>
> 2. GUIs: several of my problem sets work with simple graphics (e.g., rendering
> tessellations) or animations (e.g., a maze walk or a simplified form of
> tetris, or the game "Flow"). We have been hobbling along with the Graphics and
> Labltk modules for this but it has been more pain than my students ought to
> know. We also have some problem sets that work with audio so I would like
> support for that.
>
> Any thoughts, ideas and/or leads on either of these would be much appreciated.
> I already plan to look at js_of_ocaml more closely.
> Thank you,
> Bob Muller
>
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