Hashing a primitive data type

This recipe demonstrates how to use a simple hash function on various primitive data types.

Getting ready

Install the Data.Hashable package from Cabal as follows:

$ cabal install hashable

How to do it…

1. Import the hashing function with the following line:

   import Data.Hashable

2. Test the hash function on a string as follows; this function is actually a wrapper around the hashWithSalt function with a default salt value:

   main = do
     print $ hash "foo" 

3. Test out the hashWithSalt functions using different initial salt values as follows:

     print $ hashWithSalt 1 "foo"
     print $ hashWithSalt 2 "foo"

4. We can also hash tuples and lists as follows:

     print $ hash [ (1 :: Int, "hello", True)
                  , (0 :: Int, "goodbye", False) ]

5. Notice in the following output how the first three hashes produce different results even though their input is the same:

   $ runhaskell Main.hs
   
   7207853227093559468
   367897294438771247
   687941543139326482
   6768682186886785615

How it works…

Hashing with a salt...