On Thu, 2008-01-31 at 21:03 +0100, Bünzli Daniel wrote:
> Le 31 janv. 08 à 15:09, Andrej Bauer a écrit :
> 
> > I have become to prefer option types as return values (as opposed to  
> > exceptions), but I admit it can be annoying to always consider both  
> > possibilities, especially if you know that "None" won't happen.
> 
> Maybe it is a point of view, you are fed up of considering both  
> possibilites while I'm personally fed up of writing
> 
> match try Some (f x) with e -> None with
> | None -> ..
> | Some v -> ...
> 
> Because I need tail recursive functions.

What about a generic 

type result 'r 'e =
    | Success of 'r  (**The operation was a success*)
    | Failure of 'e  (**The operation was a failure*) 

let purify e = 
    try 
      Success ( Lazy.force e )
    with 
      exc -> Failure exc

?

With one such mechanism we can nearly automatically transform
exception-returning expressions into exceptionless management. We could
complete this with a trivial amount of Camlp4 code to avoid the call to
"lazy / Lazy.force".

What do you think about this solution ?

Cheers,
 David

-- 
David Teller
 Security of Distributed Systems
  http://www.univ-orleans.fr/lifo/Members/David.Teller
 Angry researcher: French Universities need reforms, but the LRU act
brings liquidations.