On Monday 27 August 2007 13:24:34 Daniel Bünzli wrote:
> And if you are really not a sloppy programmer you
> already have and use your own version of try/finally :
>
> let apply f x ~finally y =
>    let res = try f x with exn -> finally y; raise exn in
>    finally y;
>    res

Ironically, that's broken. :-)

If your handler "finally" raises an exception then it would replace the Abort 
exception. You should ignore any exception raised by "finally" if "f" raises 
an exception.

> Anyway most of the things I would like to cancel are not functions
> dealing with channels or locks but functions that do perform
> intensive numerical computations. In the presence of a human user you
> cannot let the ui hang for arbitrary long period of time, he should
> be able to cancel if he gets bored.

Then write in CPS and weave an abortable continuation between each step.

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
OCaml for Scientists
http://www.ffconsultancy.com/products/ocaml_for_scientists/?e