#5593: Proposal: Remove Num superclass of Bits
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Reporter: basvandijk | Owner:
Type: task | Status: new
Priority: normal | Component: libraries/base
Version: 7.2.1 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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This ticket summarizes the
[http://www.haskell.org/pipermail/libraries/2011-October/016899.html
discussion] on the proposal to remove the `Num` superclass of the `Bits`
type class.
The proposal is to:
* Remove the `Num` superclass of the `Bits` type class.
* Remove the default implementations of `bit`, `testBit` and `popCount`
since they use methods of `Num`.
* Export the following convenience functions from `Data.Bits`:
{{{
bitDefault :: (Bits a, Num a) => Int -> a
bitDefault i = 1 `shiftL` i
testBitDefault :: (Bits a, Num a) => a -> Int -> Bool
testBitDefault x i = (x .&. bit i) /= 0
popCountDefault :: (Bits a, Num a) => a -> Int
popCountDefault = go 0
where
go !c 0 = c
go c w = go (c+1) (w .&. w - 1) -- clear the least significant
}}}
Attached are tickets for `base` and `ghc`.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5593>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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