Re: [Caml-list] Uncaught exceptions in function type.

[Philippe Veber <philippe.veber@gmail.com>]

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Thanks a lot Thomas, this is certainly enough to satisfy my curiosity!


2014-05-26 17:33 GMT+02:00 Thomas Blanc <thomas.blanc@crans.org>:

> Le 26/05/2014 16:23, Philippe Veber a écrit :
>
>  Hi everyone,
>>
>> Out of curiosity, I was wondering how difficult it would be in theory to
>> extend the type system so that exceptions that can pop out of a function
>> when it is called would be included in the type of the function. Could this
>> type information be infered automatically? Could this be used to have an
>> exhaustivity check in the "with" part of a try ... with expression?
>>
>> I guess that if it was so easy, we would already be enjoying it within
>> our favorite compiler, but I fail to see how hairy is the question.
>>
>> Cheers,
>>   Philippe.
>>
>>
>>
> This as already been analyzed by François Pessaux and Xavier Leroy, see
> [1] that does a very good survey on the matter.
>
> The main problem for it is (as Romain pointed out) the problem of
> higher-order functions:
> you would have to reannotate all of your .mli to add the exception
> annotations.
> ([1] solved it by doing a separate type analysis)
>
> This would lead to a lot of problems (along with breaking existing code):
> * "exceptions we know won't be throwed":
> Typing analysis can't know that "x/2" or a.((Array.length a) - 1) wouldn't
> raise anything, so you'd have a lot of unexpected
> exceptions that would come up.
> * An arbitrary big number of exceptions
> At the time [1] was wrote, there was necessarily a finite number of
> exceptions in your program, with nifty stuff like first class modules and
> generative functors it is no longer the case.
>
> [1] http://pauillac.inria.fr/~xleroy/publi/exceptions-popl.ps.gz
>
>
>
>
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