UArray for newtypes (LogFloat)

[Don Stewart]

bulat.ziganshin:
> Hello Felipe,
> 
> Saturday, March 7, 2009, 4:22:04 PM, you wrote:
> 
> > So, I would like to make an UArray of LogFloat. They are a newtype of Double
> 
> this is possible in UArray reimplementation done in ArrayRef library
> http://haskell.org/haskellwiki/Library/ArrayRef
> although the library itself may be not compatible with ghc 6.10.
> try to search on hackage
> 

Can't you also just using generic newtype deriving?

E.g. a UArr instance for free:

    {-# LANGUAGE GeneralizedNewtypeDeriving #-}

    import Data.Array.Vector

    newtype LogFloat = LogFloat Double
        deriving (Eq,Ord,Show,Num,UA)

    main = print . sumU $ replicateU 1000 (LogFloat pi) 


Which, btw, still triggers all the usual fusion:

    $wfold :: Double# -> Int# -> Double#

    $wfold =
      \ (ww_s14A :: Double#) (ww1_s14E :: Int#) ->
        case ww1_s14E of wild_B1 {
          __DEFAULT ->
            $wfold
              (+## ww_s14A 3.141592653589793) (+# wild_B1 1);
          1000 -> ww_s14A


$ time ./A
LogFloat 3141.5926535897806
./A  0.00s user 0.00s system 154% cpu 0.004 total


-- Don