Re: [GHC] #472: Supertyping of classes

#472: Supertyping of classes
-------------------------------------+--------------------------------------
 Reporter:  nobody                   |          Owner:  nobody  
     Type:  feature request          |         Status:  assigned
 Priority:  normal                   |      Milestone:  _|_     
Component:  Compiler (Type checker)  |        Version:  None    
 Severity:  minor                    |     Resolution:  None    
 Keywords:                           |     Difficulty:  Unknown 
 Testcase:  N/A                      |   Architecture:  Unknown 
       Os:  Unknown                  |  
-------------------------------------+--------------------------------------
Changes (by igloo):

  * architecture:  => Unknown
  * difficulty:  => Unknown
  * component:  None => Compiler (Type checker)
  * milestone:  => _|_
  * testcase:  => N/A
  * os:  => Unknown

Old description:

> {{{
> see "Supertyping Suggestion for Haskell"
> [url]http://repetae.net/john/recent/out/supertyping.html[/url]
>
> example:
> [code]
> class Num a <= Group a where
>         (+) :: a -> a -> a
>         negate :: a -> a
> [/code]
>
> apart from multiple inheritance, it could work like this:
>
> [code]
> import Prelude hiding ((+),negate)
> import qualified Prelude ((+),negate)
>
> class Group a where
>         (+) :: a -> a -> a
>         negate :: a -> a
>
> instance Num a => Group a where
>         (+) = (Prelude.+)
>         negate = Prelude.negate
> [/code]
>
> - coeus_at_gmx_de
>
> }}}

New description:

 see
 [http://repetae.net/john/recent/out/supertyping.html Supertyping
 Suggestion for Haskell]

 example:
 {{{
 class Num a <= Group a where
         (+) :: a -> a -> a
         negate :: a -> a
 }}}

 apart from multiple inheritance, it could work like this:

 {{{
 import Prelude hiding ((+),negate)
 import qualified Prelude ((+),negate)

 class Group a where
         (+) :: a -> a -> a
         negate :: a -> a

 instance Num a => Group a where
         (+) = (Prelude.+)
         negate = Prelude.negate
 }}}

 - coeus_at_gmx_de

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/472>
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