On Mon, May 31, 2010 at 9:30 PM, Nicolas Pouillard
<nicolas.pouillard@gmail.com> wrote:
>
> Since having all functions in all flavours can lead to hard to interface
> bloat, one should consider tiny functions to switch from a style to another.
> It tends to be easier to start from an option type in the case of Not_found
> instead of the other way around for the following reason:
>
>  * The typechecker does not remind us to catch the exception.
>  * We need a custom handler per exception.
>  * We need to take a thunk to delay the computation.
>
>  let not_found_to_option f =
>    try Some (f ())
>    with Not_found -> None
>
> On the contrary look at:
>
>  let from_option exn = function
>    | Some x -> x
>    | None -> raise exn
>
>  Example: from_option Not_found (List.find p xs)
>

I use a syntax extension that catches "Not_found" and raises a failure
instead, with the source location of the "real" offending call. I do
this mostly because OUnit catches exceptions so backtraces are of no
use. When I use the unmodified calls, I always handle Not_found right
away, close to call point -- either by directly catching it, or by
using a higher-order function, like an iterator that expects Not_found
instead of None from the callee. Anyway, I vote for "option"ising all
of the standard library and providing the function "unsome" raising a
string with source code location of its call.