Re: [Caml-list] Newbie comment on constructor syntax

[Andreas Rossberg <rossberg@mpi-sws.org>]

On 11/09/2015 07:08 PM, Gabriel Scherer wrote:
> If we gave a functional semantic to the unapplied constructor, then I
> think that good taste would mandate for the application of this
> function and the application of the constructor to be equivalent. This
> means that by choosing a tuple-taking function, we commit to the
> tuple-application syntax (that nobody likes), and that choosing a
> currified function creates an unpleasant inconsistency in the
> language.
>
> I don't know whether we could ever manage to transition to a currified
> syntax for constructors, but right now it is at least conceivable
> because the application syntax is just a concrete syntax choice, it
> does not affect typing. Turning unapplied constructor into a function
> (tuplified or currified) makes it a typing property, observable at
> specification boundaries: we cannot change it.

Hm, I see your point, but don't you already introduce that problem 
(i.e., commit to tuples) by allowing the `C x` sugar for n-ary 
constructors? Because in a world of curried constructors, `x` would not 
be typed as the tuple of arguments, but only as the first argument of 
the constructor.

/Andreas


> On Mon, Nov 9, 2015 at 6:33 PM, Alain Frisch <alain.frisch@lexifi.com> wrote:
>> On 09/11/2015 11:35, Andreas Rossberg wrote:
>>>
>>> Yes please, I would appreciate such sugar.
>>
>>
>> I've now submitted a cleaner implementation, working on both expressions and
>> patterns:
>>
>> https://github.com/ocaml/ocaml/pull/284
>>
>>> Even more I would appreciate
>>> generalising that to allowing constructors to be used as first-class
>>> expressions (i.e., unapplied "C" -> "fun (x1,...,xN) -> C (x1,...,xN)"
>>> when C is a constructor with arity > 0). I had to write some AST mapping
>>> code recently that would have vastly benefited from that.
>>
>>
>> This is not covered (and now, it could simply be "fun x -> C x" :-)).  I
>> don't see anything clever to be done on patterns for "unapplied
>> constructors", though.
>>
>>
>> Alain
>>
>>
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