Proposal: Remove Num superclass of Bits

This ticket summarizes the 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.

Trac metadata

Trac field	Value
Version	7.2.1
Type	Task
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries/base
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