Re: [Caml-list] tpyping question

[Tiphaine Turpin <tturpin@crim.ca>]

Hello,

 here is another solution, but it's not better if there are many cases


match x, 0 with
  |  `A n, _
  | `B, n -> g n
  | `C x, _ -> ...
;;




skaller wrote:

>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.
>
>
>
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