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Re: Syntax for label
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Date: -- (:)
From: Jacques Garrigue <garrigue@k...>
Subject: Re: Syntax for label, NEW PROPOSAL
Hi John,

> I think this could be made sane by a reform of how the optional
> arguments work.  There are a couple of interesting possibilities:
> # let f ?style:x _ = x;;
> - val f : ?style:('a option) -> 'b -> 'a option
> # let f (style:x : 'a option) _ = x
> - val f : style:('a option) -> 'b -> 'a option

Bingo, you've just found how it's implemented!
Omitting the option constructor for optional arguments is just
a small comfort. This can be pretty important when you have 10 or 20
optional arguments in the same function.

By the way, having a default case for a non-optional argument was
legal in O'Labl. I just didn't include it in O'Caml because I thought
I would be more confusing than useful.

> The first is dirty because there are two kinds of special arguments
> (optional and non-optional).  The second because it gets into the type
> system.  I think the second must lose, since "knowing" that something
> is an option type is complex.

In fact the distinction between optional and non-optional arguments is
useful, because it allows a nice interaction between classic and
modern mode.  Optional ones behave the same in both modes, only
non-optional ones behave differently.

> Of course, this is all radically different from O'Labl, so it will
> never happen.

I do not intend to be so exclusive...
In fact there are even a number of differences between ocaml 2.99 and
olabl, and some from you.
The only point is that O'Labl has been around for a while, and we have
had the time to test in practice that this model works, and is not
difficult to grasp. Another model would take lots of time testing

Best regards,