haskell - 值列表中的组合列表？

Question

如何从列表列表中获取组合列表？

例如：

ghci> getCombinations [[1,2,3],[10,20,30],[100,200,300]]

[[1,10,100],[1,10,200],[1,10,300],[1,20,100],[1,20,200],[1,20,300],[1,30,100],
[1,30,200],[1,30,300],[2,10,100],[2,10,200],[2,10,300],[2,20,100],[2,20,200],
[2,20,300],[2,30,100],[2,30,200],[2,30,300],[3,10,100],[3,10,200],[3,10,300],
[3,20,100],[3,20,200],[3,20,300],[3,30,100],[3,30,200],[3,30,300]]

Answer 1

import Control.Applicative

getCombinations :: [[a]] -> [[a]]
getCombinations values =
foldl (\acc values -> (\list value -> list ++ [value]) <$> acc <*> values) [[]] values

getCombinations [[1,2,3],[10,20,30],[100,200,300]]

[[1,10,100],[1,10,200],[1,10,300],[1,20,100],[1,20,200],[1,20,300],[1,30,100],[1,30,200],[ 1,30,300],[2,10,100],[2,10,200],[2,10,300],[2,20,100],[2,20,200],[2,20,300],[2,30,100],[2, 30,200],[2,30,300],[3,10,100],[3,10,200],[3,10,300],[3,20,100],[3,20,200],[3,20,300],[3,30,100] ,[3,30,200],[3,30,300]]