[Haskell-cafe] incomplete-uni-patterns

[Jeff Clites]

That was my thinking with using an explicit lazy pattern match indication:

    let ~(Just a) = …

It seems to me that this shouldn’t warn (though apparently it does), since it’s overly opting in to a non-exhaustive match.

Jeff

> On Jan 25, 2023, at 9:08 PM, David Feuer <david.feuer at gmail.com> wrote:
> 
> 
> It seems to me that instead of working around this, we should add a pragma to suppress the warning at the pattern site. Maybe something like
> 
> let
>   {-# PARTIAL_MATCH #-}
>   Just a = blah blah
> 
> That way GHC can see that you noticed the partial match and that you're okay with it.
> 
>> On Wed, Jan 25, 2023, 7:06 PM Kazu Yamamoto (山本和彦) via Haskell-Cafe <haskell-cafe at haskell.org> wrote:
>> Hello,
>> 
>> The recent GHC added incomplete-uni-patterns to the -Wall option.
>> So, we have a waning with the following code:
>> 
>>     let [addr,port] = args
>> 
>> To avoid this, I changed the code to:
>> 
>>     let addr = head args
>>         port = head $ tail args
>> 
>> In my opinion, this seems Lisp rather than Haskell.
>> 
>> Also, I need to avoid:
>> 
>>     let Just val = mval
>> 
>> Rahter, I use:
>> 
>>     let val = fromJust mval
>> 
>> This is annoying to me.
>> 
>> How do you get along with incomplete-uni-patterns?
>> I would like to know the best current practice.
>> 
>> --Kazu
>> 
>> 
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