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haskellcompressionrun-length-encoding

Compressing by counting repetitive elements (Haskell)

I'm looking for a straight-forward combination of standard higher-order functions to compress a list by counting repetitive elements. For example the result for

"abbccccb"

would be : 

 [(1, 'a'), (2, 'b'), (4, 'c'), (1, 'b')]

another example, the result for

(sort "abrakadabra")

would be:

[(5, 'a'), (2, 'b'), (1, 'd'), (1, 'k'), (2, 'r')]
Solution

  • I wrote a code that only makes use of elementary functions. 

    f :: Eq a => [a] -> [(Int, a)]
f [] = []
f (x:xs) = (1 + length (takeWhile (==x) xs), x) : f (dropWhile (==x) xs)

    I hope this will help!.