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Today's Topics:
1. Re: How to write the FromJSON instance for CUid (David McBride)
2. Re: How to write the FromJSON instance for CUid
(PICCA Frederic-Emmanuel)
3. Re: understanding function signature alignement
(simkest...@gmail.com)
----------------------------------------------------------------------
Message: 1
Date: Fri, 10 Aug 2018 07:40:18 -0400
From: David McBride <toa...@gmail.com>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: Re: [Haskell-beginners] How to write the FromJSON instance
for CUid
Message-ID:
<can+tr4247osgirusackku3kms5m6id9bja-glk+ektaimcc...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Didn't even occur to me that there would already be a Word32 instance.
Looking at the source, it absolutely deals with every case automatically.
On Fri, Aug 10, 2018 at 4:05 AM, PICCA Frederic-Emmanuel <
frederic-emmanuel.pi...@synchrotron-soleil.fr> wrote:
> Hello, and thanks for the reply
>
> What about this
>
> instance FromJSON CGid where
> parseJSON x = CGid <$> (parseJSON x :: Parser Word32)
> {-# INLINE parseJSON #-}
>
>
> Do you think that it deal with all the problem you are trying to prevent ?
>
>
> Cheers
>
> Fred
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
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Message: 2
Date: Fri, 10 Aug 2018 11:43:23 +0000
From: PICCA Frederic-Emmanuel
<frederic-emmanuel.pi...@synchrotron-soleil.fr>
To: "The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell" <beginners@haskell.org>
Subject: Re: [Haskell-beginners] How to write the FromJSON instance
for CUid
Message-ID:
<a2a20ec3b8560d408356cac2fc148e53015b311...@sun-dag3.synchrotron-soleil.fr>
Content-Type: text/plain; charset="us-ascii"
> Didn't even occur to me that there would already be a Word32 instance.
> Looking at the source, it absolutely deals with every case automatically.
Great,
now the real question ;)
I use Generic with aeson and I endup like plenty of other with these orphan
instances definietion.
what is the right way to deal with this.
fill a bug against all these types and request instances for these typeclass.
or ?
Cheers
Fred
------------------------------
Message: 3
Date: Fri, 10 Aug 2018 14:25:56 +0200
From: "simkest...@gmail.com" <simkest...@gmail.com>
To: Hask begginers <beginners@haskell.org>
Subject: Re: [Haskell-beginners] understanding function signature
alignement
Message-ID:
<CAJqT=ykke-sn5afpo_u5+8dw4hokmdahdgzqxg80ykbxpsv...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Yes, thinking it the terms that something which is absolutely free to be
whatever, can be restricted and reduced into something else while other way
around is not possible is usefull;
thanks
On Fri, Aug 10, 2018 at 12:06 PM Theodore Lief Gannon <tan...@gmail.com>
wrote:
> You're right that the return type is more restricted than the argument,
> but it's in an *absolute* sense, not a relative one. It's not possible to
> relax `m d` to make it the same type as `c`, but it IS possible to
> constrain `c` to be the same as `m d`! And that's how `id` works here: the
> input in this case is known to be the same type as the output. You need
> something wrapped in a monad, and you already have that, so you just use it
> as-is.
>
> On Thu, Aug 9, 2018, 7:22 AM simkest...@gmail.com <simkest...@gmail.com>
> wrote:
>
>> Thanks, it is still a bit fuzzy to me ...
>>
>>
>> I understand what you did but what confuses me is that when i look at
>> function with signature like
>>
>> f :: Monad m => c -> m d
>>
>> I always think that return type is somehow restricted in comparison to
>> input because it demands that output type is wraped inside something (monad
>> in this case).
>>
>> For such signature to fit id signature (a -> a) , c type shoud be also
>> wraped inside monad but it is not case here...
>>
>> Anyhow, I still have to figure it out
>>
>> thanks
>> _______________________________________________
>> Beginners mailing list
>> Beginners@haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
> _______________________________________________
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>
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