Re: [Caml-list] exhaustiveness checking within a submatch

[Martin DeMello <martindemello@gmail.com>]

Thanks. So I guess the answer boils down to "possible but not worth
it", which makes sense.

martin

On Thu, Oct 10, 2013 at 1:09 AM, David House <dhouse@janestreet.com> wrote:
> This does actually work with polymorphic variants, as long as you
> rename the thing in the submatch:
>
> match f with `A -> 1 | `B -> 2 | (`C | `D as foo) -> match foo with `C
> -> 3 | `D -> 4
>
> On 10 October 2013 09:07, David Allsopp <dra-news@metastack.com> wrote:
>> Martin DeMello wrote:
>>> Just curious as to why the compiler can't handle this, since in theory
>>> everything is statically deducible:
>>>
>>> # type test = A | B | C | D;;
>>> type test = A | B | C | D
>>>
>>> # let f = A;;
>>> val f : test = A
>>>
>>> # match f with A -> 1 | B -> 2 | C | D -> ( match f with C -> 3 | D ->
>>> 4);;
>>> Characters 40-71:
>>>                                                                Warning
>>> 8: this pattern-matching is not exhaustive.
>>>                                                        Here is an
>>> example of a value that is not matched:
>>> (A|B)
>>> Characters 40-71:
>>> Warning 8: this pattern-matching is not exhaustive.
>>> Here is an example of a value that is not matched:
>>> (A|B)
>>> - : int = 1
>>
>> http://caml.inria.fr/pub/ml-archives/caml-list/2007/02/d35648b13d76f1717edbf41101dc913f.en.html
>>
>>
>> David
>>
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