Version française
Home     About     Download     Resources     Contact us    
Browse thread
pattern matching and records vs tuples
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: -- (:)
From: Pal-Kristian Engstad <pal_engstad@n...>
Subject: Re: [Caml-list] pattern matching and records vs tuples
Honestly, I'd prefer to have to annotate non-exhaustive records:

    let { foo = foo; bar = bar } = x

should only match { foo; bar }, but

    let { foo = foo; bar =  bar; .. } = x,

can match records with more labels.

PKE.

Yaron Minsky wrote:
> On Tue, Apr 14, 2009 at 10:12 AM, Yoann Padioleau <padator@wanadoo.fr 
> <mailto:padator@wanadoo.fr>> wrote:
>
>
>     So, would it be possible to extend the ocaml compiler with a simple
>     feature that let the programmer tell the compiler when he use
>     an "exhaustive" pattern with record, e.g.
>
>      let foo = function
>      { field1 = v1; field2 = v2; NOTHING_ELSE} ->
>
>
> I think this is a great idea (and something I've blogged about before, 
> as Christophe Troestler points out).  The thing I've never come up 
> with a good proposal for is what would be a pleasant syntax to 
> indicate the exhaustiveness of the pattern match.  I could imagine 
> something terse like this:
>
>    let {! foo = foo; bar = bar; } = x
>
> where the ! indicates that the pattern match should be exhaustive.  
> Such terse notation would sadly be somewhat obscure.
>
> Another thought I've had for making record matches lighter is to do 
> the same kind of trick that's done with labeled arguments, i.e., have
>
>    let { foo; bar } = x
>
> bind the variable foo to the x.foo, and bind bar to x.bar.   
> Similarly, it might be nice for:
>
>     let foo = 3 and bar = 3. in { foo;bar }
>
> to be equivalent to
>
>    let foo = 3 and bar = 3. in { foo = foo; bar = bar }
>
> y
>


-- 
Pål-Kristian Engstad (engstad@naughtydog.com), 
Lead Graphics & Engine Programmer,
Naughty Dog, Inc., 1601 Cloverfield Blvd, 6000 North,
Santa Monica, CA 90404, USA. Ph.: (310) 633-9112.

"Emacs would be a far better OS if it was shipped with 
 a halfway-decent text editor." -- Slashdot, Dec 13. 2005.