Functional Programming MT22, Common functions
Flashcards
Can you give the definition of cp (cartesian product) in Haskell (not as a fold)?
cp (cartesian product) in Haskell (not as a fold)?cp :: [[a]] -> [[a]]
cp [] = [[]]
cp (xs:xss) = [x:ys | x <- xs, ys <- cp xss]
Can you give the definition of subsets which returns all the subsets of a given list in Haskell (not a fold)?
subsets which returns all the subsets of a given list in Haskell (not a fold)?subsets :: [a] -> [[a]]
subsets [] = [[]]
subsets (x:xs) = [zs | ys <- subsets xs, zs <- [ys, (x:ys)]]
Can you give the definition of subsetsN which returns all the subsets of a list with size exactly n in Haskell?
subsetsN which returns all the subsets of a list with size exactly n in Haskell?subsetsN :: Int -> [a] -> [[a]]
subsetsN 0 _ = [[]]
subsetsN _ [] = []
subsetsN n (x:xs) =
[ x:ys | ys <- subsetsN (n-1) xs ]
++ subsetsN n xs
Can you give the definition of filterDups which removes all duplicate elements from a list in Haskell?
filterDups which removes all duplicate elements from a list in Haskell?filterDups :: Eq a => [a] -> [a]
filterDups xs = filterDups' xs []
where filterDups' [] _ = []
filterDups' (x:xs) seen
| x `elem` seen = filterDups' xs seen
| otherwise = x:filterDups' xs (x:seen)
Can you give the definition of transpose which transposes a multidimensional list in Haskell?
transpose which transposes a multidimensional list in Haskell?transpose :: [[a]] -> [[a]]
transpose xss
| all null xss = []
| otherwise = col xss : transpose (map tail xss)
where col = map head