On Mon, 31 May 2010 16:36:22 +0200, Goswin von Brederlow <goswin-...@web.de> wrote: > Richard Jones <r...@annexia.org> writes: > > > On Wed, May 26, 2010 at 06:15:05PM +0200, Hans Ole Rafaelsen wrote: > >> What experience does people have to using alternatives to exceptions, such > >> as option types or exception monads? Does use of third part libraries that > >> still throws exceptions make such approaches hard to use? Performance wise > >> it seems to be comparable to catching exceptions or matching for options, > >> so > >> I guess the difference be might a question of programming style? > > > > Personally I've found that you should only throw those exceptions > > which can be caught in a single place in the program. By this I mean > > that an exception such as Not_found shouldn't be thrown, and instead > > it would be better to use an option type (for stdlib functions which > > throw Not_found, you have to be _very_ careful that the exception > > cannot "escape"). > > Which needlessly complicates your code when it never happens. > > Imho a good module should provide both an exception and option based > interface to fit the circumstances and programming style.
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) Best regards, -- Nicolas Pouillard http://nicolaspouillard.fr _______________________________________________ Caml-list mailing list. Subscription management: http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list Archives: http://caml.inria.fr Beginner's list: http://groups.yahoo.com/group/ocaml_beginners Bug reports: http://caml.inria.fr/bin/caml-bugs