リストモナドの非決定性

ってこういうやつの事？

nonDet :: [Int] -> [Int] -> [Int]
nonDet [] _ = []
nonDet _ [] = []
nonDet xs ys = [(x + y)| x <- xs, y <- ys]

モナド風味で書くと

nonDet2 :: [Int] -> [Int] -> [Int]
nonDet2 [] _ = []
nonDet2 _ [] = []
nonDet2 xs ys = do
	x <- xs
	y <- ys
	return (x + y)

実行すると

Main> nonDet [1..3] [1..4]
[2,3,4,5,3,4,5,6,4,5,6,7]

みたいな。
んー…

てか、

Haskellのコード久々に書いた、俺ｗ