Version française
Home     About     Download     Resources     Contact us    
Browse thread
[Caml-list] tpyping question
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: -- (:)
From: skaller <skaller@o...>
Subject: Re: [Caml-list] tpyping question
On Mon, 2003-08-11 at 15:18, Karl Zilles wrote:
> skaller wrote:
> > BTW: something I've needed is like this:
> > 
> > type [`A of int * int | `B of int]
> > let f x = match x with
> > | `A (i,j)
> > | `B i with j=0 -> ....
> > (*     ********   *)
> > 
> > At the moment, I have to code this as:
> > 
> > let f x =
> >   let g i j = ... in
> >   match x with
> >   | `A (i,j) -> g i j
> >   | `B i -> g i 0
> > 
> > delocalising the case handling code.
> > 
> 
> Wouldn't it be more natural to write:
> 
> let f x =
>     let (i,j) = match x with
> 	| `A v -> v
>          | `B u -> (u,0) in
>     ...

In reality there are 20 tags, not just the 2 shown.
So I'd have to write:

match x with
| .....
| `A _ as y 
| `B _ as y -> let (i,j) = match y with `A v->v | `B u -> (u,0) in ...
| ......

repeating the tags, In fact I do this sometimes, but it's also poor
style repeating the tags. So I have 2 choices of poor style:
repeat tags or delocalise handler, hence my suggestion,
in which the handler is local and there's no repetition.



-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners