selection sort

selectionsort.hs

import Data.List
import Test.QuickCheck

selectionSort :: Ord a => [a] -> [a]
selectionSort [] = []
selectionSort xs = v : (selectionSort (extract i xs))
  where
    (v, i) = findMin xs

findMin :: Ord a => [a] -> (a, Int)
findMin = minimumBy compare . numbering

numbering :: [a] -> [(a, Int)]
numbering xs = zip xs [0..]
    
extract :: Int -> [a] -> [a]
extract n xs = ys ++ stail zs
  where
    (ys, zs) = splitAt n xs 
    stail []     = []
    stail (_:rs) = rs

prop_selectionSort :: [Int] -> Bool
prop_selectionSort xs = selectionSort xs == sort xs