From yom at artyom.me  Tue Apr 21 13:26:41 2015
From: yom at artyom.me (Artyom)
Date: Tue, 21 Apr 2015 16:26:41 +0300
Subject: [jhc] A possible bug with constraints being perceived as
 multiparameter type classes
Message-ID: <55365011.8070508@artyom.me>

This (empty) instance declaration

|instance  Num  (a,b)  =>Num  (a,b,Int)  where
|

produces the following error when compiled with jhc 0.8.2:

|$ Temp/jhc-0.8.2/jhc Temp/jhc1.hs

jhc Temp/jhc1.hs
jhc 0.8.2 (mydniquipepo-32)
Finding Dependencies...
Using Ho Cache: '/home/yom/.jhc/cache'

Temp/jhc1.hs:1   - Error: Invalid Class. multiparameter classes not yet supported:
(Num,[HsTyTuple [HsTyVar {hsTypeName = a},HsTyVar {hsTypeName = b}]])
|

Am I misunderstanding something, or is it a legitimate bug?

?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/jhc/attachments/20150421/9e3972fa/attachment.html>

From allbery.b at gmail.com  Tue Apr 21 13:38:26 2015
From: allbery.b at gmail.com (Brandon Allbery)
Date: Tue, 21 Apr 2015 09:38:26 -0400
Subject: [jhc] A possible bug with constraints being perceived as
 multiparameter type classes
In-Reply-To: <55365011.8070508@artyom.me>
References: <55365011.8070508@artyom.me>
Message-ID: <CAKFCL4VUGf=nygcx-Dvb0woWAKKQ_rDZ6Tsa9Ba0VFMvyN9GGw@mail.gmail.com>

On Tue, Apr 21, 2015 at 9:26 AM, Artyom <yom at artyom.me> wrote:

>  $ Temp/jhc-0.8.2/jhc Temp/jhc1.hs
>
> jhc Temp/jhc1.hs
> jhc 0.8.2 (mydniquipepo-32)
> Finding Dependencies...
> Using Ho Cache: '/home/yom/.jhc/cache'
>
> Temp/jhc1.hs:1   - Error: Invalid Class. multiparameter classes not yet supported:
> (Num,[HsTyTuple [HsTyVar {hsTypeName = a},HsTyVar {hsTypeName = b}]])
>
> Am I misunderstanding something, or is it a legitimate bug?
> ?
>

Looks multiparameter to me:

    instance ... => Num (T a b Int) where

with T ~ (,,). Which is what the second line of the error message is
telling you, more or less.

-- 
brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/jhc/attachments/20150421/20c85a9c/attachment.html>

From yom at artyom.me  Tue Apr 21 13:45:44 2015
From: yom at artyom.me (Artyom)
Date: Tue, 21 Apr 2015 16:45:44 +0300
Subject: [jhc] Is there a working example of type families usage?
Message-ID: <55365488.2000805@artyom.me>

I tried this:

|{-# LANGUAGE TypeFamilies #-}

class  C  xwhere
   type  A  x
|

It fails with this error:

|Temp/jhc1.hs:4   - Error: parse error at "}"
|

Standalone type families don?t work either:

|{-# LANGUAGE TypeFamilies #-}

type  family  A  x
|

|Temp/jhc1.hs:3   - Error: parse error at "family"
|

Is there an example somewhere that I missed while googling?

?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/jhc/attachments/20150421/d9909336/attachment.html>

From roma at ro-che.info  Tue Apr 21 14:09:57 2015
From: roma at ro-che.info (Roman Cheplyaka)
Date: Tue, 21 Apr 2015 17:09:57 +0300
Subject: [jhc] A possible bug with constraints being perceived as
 multiparameter type classes
In-Reply-To: <CAKFCL4VUGf=nygcx-Dvb0woWAKKQ_rDZ6Tsa9Ba0VFMvyN9GGw@mail.gmail.com>
References: <55365011.8070508@artyom.me>
 <CAKFCL4VUGf=nygcx-Dvb0woWAKKQ_rDZ6Tsa9Ba0VFMvyN9GGw@mail.gmail.com>
Message-ID: <55365A35.9040208@ro-che.info>

On 21/04/15 16:38, Brandon Allbery wrote:
> On Tue, Apr 21, 2015 at 9:26 AM, Artyom <yom at artyom.me
> <mailto:yom at artyom.me>> wrote:
> 
>     |$ Temp/jhc-0.8.2/jhc Temp/jhc1.hs 
> 
>     jhc Temp/jhc1.hs
>     jhc 0.8.2 (mydniquipepo-32)
>     Finding Dependencies...
>     Using Ho Cache: '/home/yom/.jhc/cache'
> 
>     Temp/jhc1.hs:1   - Error: Invalid Class. multiparameter classes not yet supported:
>     (Num,[HsTyTuple [HsTyVar {hsTypeName = a},HsTyVar {hsTypeName = b}]])
>     |
> 
>     Am I misunderstanding something, or is it a legitimate bug?
> 
>     ?
> 
> 
> Looks multiparameter to me:
> 
>     instance ... => Num (T a b Int) where
> 
> with T ~ (,,). Which is what the second line of the error message is
> telling you, more or less.

No, it's a multi-parameter type, but a single-parameter class.

Multi-parameter would be Num a b Int.

Roman


From roma at ro-che.info  Tue Apr 21 14:12:05 2015
From: roma at ro-che.info (Roman Cheplyaka)
Date: Tue, 21 Apr 2015 17:12:05 +0300
Subject: [jhc] A possible bug with constraints being perceived as
 multiparameter type classes
In-Reply-To: <55365A35.9040208@ro-che.info>
References: <55365011.8070508@artyom.me>
 <CAKFCL4VUGf=nygcx-Dvb0woWAKKQ_rDZ6Tsa9Ba0VFMvyN9GGw@mail.gmail.com>
 <55365A35.9040208@ro-che.info>
Message-ID: <55365AB5.1040203@ro-che.info>

On 21/04/15 17:09, Roman Cheplyaka wrote:
> On 21/04/15 16:38, Brandon Allbery wrote:
>> On Tue, Apr 21, 2015 at 9:26 AM, Artyom <yom at artyom.me
>> <mailto:yom at artyom.me>> wrote:
>>
>>     |$ Temp/jhc-0.8.2/jhc Temp/jhc1.hs 
>>
>>     jhc Temp/jhc1.hs
>>     jhc 0.8.2 (mydniquipepo-32)
>>     Finding Dependencies...
>>     Using Ho Cache: '/home/yom/.jhc/cache'
>>
>>     Temp/jhc1.hs:1   - Error: Invalid Class. multiparameter classes not yet supported:
>>     (Num,[HsTyTuple [HsTyVar {hsTypeName = a},HsTyVar {hsTypeName = b}]])
>>     |
>>
>>     Am I misunderstanding something, or is it a legitimate bug?
>>
>>     ?
>>
>>
>> Looks multiparameter to me:
>>
>>     instance ... => Num (T a b Int) where
>>
>> with T ~ (,,). Which is what the second line of the error message is
>> telling you, more or less.
> 
> No, it's a multi-parameter type, but a single-parameter class.
> 
> Multi-parameter would be Num a b Int.
> 
> Roman

That said, it's not H98 either (ghc would require FlexibleInstances), so
jhc may be right in rejecting in, just not explaining it properly.

Roman

From jhc at henning-thielemann.de  Tue Apr 21 19:02:28 2015
From: jhc at henning-thielemann.de (Henning Thielemann)
Date: Tue, 21 Apr 2015 21:02:28 +0200 (CEST)
Subject: [jhc] Is there a working example of type families usage?
In-Reply-To: <55365488.2000805@artyom.me>
References: <55365488.2000805@artyom.me>
Message-ID: <alpine.DEB.2.02.1504212101410.7195@sputnik>


On Tue, 21 Apr 2015, Artyom wrote:

> I tried this:
> 
> {-# LANGUAGE TypeFamilies #-}
> 
> class C x where
>   type A x
> 
> It fails with this error:
> 
> Temp/jhc1.hs:4   - Error: parse error at "}"


Does JHC already support type families?