skaller <skaller@ozemail.com.au> writes:

> 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 ...
> | ......

If `A (x,y) and `B x have a link (as it seem in your
example) I would have define the type 

type aorB = [`A of int * int | `B of int]

and then your code become :

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

by the way, you only need one as for the | `A ... | `B ... pattern
there is only one as, not two . 

>
> 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, 

repeat tags is the best way IMHO (to avoid to correct the bugs in only
one of the two branch).

-- 
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat

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