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List:       haskell-cafe
Subject:    [Haskell-cafe] [uvector] derive UA instance for newtype
From:       Khudyakov Alexey <alexey.skladnoy () gmail ! com>
Date:       2009-09-23 18:58:57
Message-ID: 200909232304.58119.alexey.skladnoy () gmail ! com
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Hello

I want to derive UA instance for newtypes. 

Say I have following newtype:
> newtype Foo a = Foo a

Attempts to derive UA automatically fails because it have associated types. It 
seems that it's not possible to define from outside. However it's possible to 
derive instance in the uvector's internals. 

> deriving instance UAE a   => UAE (Foo a)
> deriving instance UPrim a => UPrim (Foo a)
> 
> instance UPrim a => UA (Foo a) where
>   newtype UArr  (Foo a)   = UAFoo (BUArr (Foo a))
>   newtype MUArr (Foo a) s = MUFoo (MBUArr s (Foo a))
> 
>   lengthU        = primLengthU
>   indexU         = primIndexU
>   sliceU         = primSliceU
>   lengthMU       = primLengthMU
>   newMU          = primNewMU
>   readMU         = primReadMU
>   writeMU        = primWriteMU
>   copyMU         = primCopyMU
>   unsafeFreezeMU = primUnsafeFreezeMU
> 
>   memcpyMU     = primMemcpyMU
>   memcpyOffMU  = primMemcpyOffMU
>   memmoveOffMU = primMemmoveOffMU

Am I moving in right direction and are there other/better solutions to 
problem?

--
  Khudyakov Alexey
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