| Safe Haskell | Safe |
|---|---|
| Language | Haskell2010 |
Hashable
Contents
Synopsis
- class Hashable a where
- hashUsing :: Hashable b => (a -> b) -> Int -> a -> Int
- hashPtr :: Ptr a -> Int -> IO Int
- hashPtrWithSalt :: Ptr a -> Int -> Int -> IO Int
- hashByteArray :: ByteArray# -> Int -> Int -> Int
- hashByteArrayWithSalt :: ByteArray# -> Int -> Int -> Int -> Int
- data Hashed a
- hashed :: Hashable a => a -> Hashed a
- unhashed :: Hashed a -> a
- mapHashed :: Hashable b => (a -> b) -> Hashed a -> Hashed b
- traverseHashed :: (Hashable b, Functor f) => (a -> f b) -> Hashed a -> f (Hashed b)
Hashable
The class of types that can be converted to a hash value.
Minimal implementation: hashWithSalt.
Methods
hashWithSalt :: Int -> a -> Int infixl 0 #
Return a hash value for the argument, using the given salt.
The general contract of hashWithSalt is:
- If two values are equal according to the
==method, then applying thehashWithSaltmethod on each of the two values must produce the same integer result if the same salt is used in each case. - It is not required that if two values are unequal
according to the
==method, then applying thehashWithSaltmethod on each of the two values must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal values may improve the performance of hashing-based data structures. - This method can be used to compute different hash values for
the same input by providing a different salt in each
application of the method. This implies that any instance
that defines
hashWithSaltmust make use of the salt in its implementation.
Like hashWithSalt, but no salt is used. The default
implementation uses hashWithSalt with some default salt.
Instances might want to implement this method to provide a more
efficient implementation than the default implementation.
Instances
Transform a value into a Hashable value, then hash the
transformed value using the given salt.
This is a useful shorthand in cases where a type can easily be
mapped to another type that is already an instance of Hashable.
Example:
data Foo = Foo | Bar
deriving (Enum)
instance Hashable Foo where
hashWithSalt = hashUsing fromEnumCompute a hash value for the content of this pointer.
Compute a hash value for the content of this pointer, using an initial salt.
This function can for example be used to hash non-contiguous segments of memory as if they were one contiguous segment, by using the output of one hash as the salt for the next.
Arguments
| :: ByteArray# | data to hash |
| -> Int | offset, in bytes |
| -> Int | length, in bytes |
| -> Int | hash value |
Compute a hash value for the content of this ByteArray#,
beginning at the specified offset, using specified number of bytes.
Arguments
| :: ByteArray# | data to hash |
| -> Int | offset, in bytes |
| -> Int | length, in bytes |
| -> Int | salt |
| -> Int | hash value |
Compute a hash value for the content of this ByteArray#, using
an initial salt.
This function can for example be used to hash non-contiguous segments of memory as if they were one contiguous segment, by using the output of one hash as the salt for the next.
A hashable value along with the result of the hash function.
Instances
| Foldable Hashed | |
Defined in Data.Hashable.Class Methods fold :: Monoid m => Hashed m -> m # foldMap :: Monoid m => (a -> m) -> Hashed a -> m # foldr :: (a -> b -> b) -> b -> Hashed a -> b # foldr' :: (a -> b -> b) -> b -> Hashed a -> b # foldl :: (b -> a -> b) -> b -> Hashed a -> b # foldl' :: (b -> a -> b) -> b -> Hashed a -> b # foldr1 :: (a -> a -> a) -> Hashed a -> a # foldl1 :: (a -> a -> a) -> Hashed a -> a # elem :: Eq a => a -> Hashed a -> Bool # maximum :: Ord a => Hashed a -> a # minimum :: Ord a => Hashed a -> a # | |
| Eq1 Hashed | |
| Ord1 Hashed | |
Defined in Data.Hashable.Class | |
| Show1 Hashed | |
| Hashable1 Hashed | |
Defined in Data.Hashable.Class | |
| Eq a => Eq (Hashed a) | Uses precomputed hash to detect inequality faster |
| Ord a => Ord (Hashed a) | |
Defined in Data.Hashable.Class | |
| Show a => Show (Hashed a) | |
| (IsString a, Hashable a) => IsString (Hashed a) | |
Defined in Data.Hashable.Class Methods fromString :: String -> Hashed a # | |
| Hashable (Hashed a) | |
Defined in Data.Hashable.Class | |
| NFData a => NFData (Hashed a) | |
Defined in Data.Hashable.Class | |
traverseHashed :: (Hashable b, Functor f) => (a -> f b) -> Hashed a -> f (Hashed b) #
Hashed cannot be Traversable