exploring huffman coding

huffman-ghci.hs

-- build huffman coding tree from text input
ghci> buildTree "recurse center"
Branch
  (Branch
     (Branch
        (Leaf (Frequency {char = 'u', count = 1}))
        (Branch
           (Leaf (Frequency {char = 's', count = 1}))
           (Leaf (Frequency {char = 't', count = 1}))))
     (Leaf (Frequency {char = 'r', count = 3})))
  (Branch
     (Branch
        (Branch
           (Leaf (Frequency {char = ' ', count = 1}))
           (Leaf (Frequency {char = 'n', count = 1})))
        (Leaf (Frequency {char = 'c', count = 2})))
     (Leaf (Frequency {char = 'e', count = 4})))

-- interpret huffman tree -> dictionary
ghci> coding $ buildTree "recurse center"
[('u',"000"),('s',"0010"),('t',"0011"),('r',"01"),(' ',"1000"),('n',"1001"),('c',"101"),('e',"11")]

-- translate input to binary
ghci> let input = "recurse center"; tree = buildTree input in translate (coding tree) input
"011110100001001011100010111100100111101"

-- grab binary string
ghci> let binary = (let input = "recurse center"; tree = buildTree input in translate (coding tree) input)

-- split bits into bytes
ghci> unfoldr grabByte binary
["01111010","00010010","11100010","11110010","0111101"]

-- each byte in decimal
ghci> let bytes = unfoldr grabByte binary in fst <$> concatMap (Numeric.readBin @Int) bytes
[122,18,226,242,61]