diff options
| -rw-r--r-- | libraries/base/Data/Bits.hs | 32 |
1 files changed, 25 insertions, 7 deletions
diff --git a/libraries/base/Data/Bits.hs b/libraries/base/Data/Bits.hs index 67772df563..95105a4b3f 100644 --- a/libraries/base/Data/Bits.hs +++ b/libraries/base/Data/Bits.hs @@ -71,8 +71,14 @@ import GHC.Show -- >>> complement oneBits :: Word == zeroBits :: Word -- True -- +-- = Note +-- +-- The constraint on 'oneBits' is arguably too strong. However, as some types +-- (such as 'Natural') have undefined 'complement', this is the only safe +-- choice. +-- -- @since 4.16 -oneBits :: (Bits a) => a +oneBits :: (FiniteBits a) => a oneBits = complement zeroBits {-# INLINE oneBits #-} @@ -99,8 +105,12 @@ newtype And a = And { getAnd :: a } instance (Bits a) => Semigroup (And a) where And x <> And y = And (x .&. y) --- | @since 4.16 -instance (Bits a) => Monoid (And a) where +-- | This constraint is arguably too strong. However, +-- as some types (such as 'Natural') have undefined 'complement', this is the +-- only safe choice. +-- +-- @since 4.16 +instance (FiniteBits a) => Monoid (And a) where mempty = And oneBits -- | Monoid under bitwise inclusive OR. @@ -177,10 +187,18 @@ newtype Iff a = Iff { getIff :: a } Read -- ^ @since 4.16 ) --- | @since 4.16 -instance (Bits a) => Semigroup (Iff a) where +-- | This constraint is arguably +-- too strong. However, as some types (such as 'Natural') have undefined +-- 'complement', this is the only safe choice. +-- +-- @since 4.16 +instance (FiniteBits a) => Semigroup (Iff a) where Iff x <> Iff y = Iff . complement $ (x `xor` y) --- | @since 4.16 -instance (Bits a) => Monoid (Iff a) where +-- | This constraint is arguably +-- too strong. However, as some types (such as 'Natural') have undefined +-- 'complement', this is the only safe choice. +-- +-- @since 4.16 +instance (FiniteBits a) => Monoid (Iff a) where mempty = Iff oneBits |