Re: [Caml-list] exn vs option

[David House <dhouse@janestreet.com>]

On Wed, Apr 11, 2012 at 11:32 AM, David House <dhouse@janestreet.com> wrote:
> On Wed, Apr 11, 2012 at 11:26 AM, Goswin von Brederlow
> <goswin-v-b@web.de> wrote:
>>> However in the particular case of finding something in a data structure where the user could be confronted with a situation where he can prove that the datum will be found I think it's justified to provide both flavours. For these cases, in my own code I settled on the following pattern :
>>>
>>>     val find : 'a t -> key -> 'a option
>>>     (** [find d k] is the value bound to [k] in [d], if any. *)
>>>
>>>     val get : 'a t -> key -> 'a
>>>     (** [get d k] is like {!find} but raises [Invalid_argument] if [k] is not bound in [d]. *)
>>
>> That pattern works well if you have just one or few such functions and
>> can think of nice names to differentiate them.
>
> A common pattern that is convenient and clear is to append _exn to the
> functions that raise excetions on failure.

As an example, see Core's Map module:

https://bitbucket.org/yminsky/ocaml-core/src/c0e9df7b574d/base/core/lib/core_map_intf.ml

We have, e.g., [find] and [find_exn].