folds

hfold.hs

-- this
foldr (\x xs -> (x * 10):xs) [] $ foldr (\x xs -> if x `mod` 2 == 0 then x:xs else xs) [] $ foldr (\x xs -> if x > 3 then x:xs else xs) [] [5,9,8,3,6,7,1,5,2]

-- that
[x * 10 | x <- [5,9,8,3,6,7,1,5,2], x > 3, x `mod` 2 == 0]

-- or
foldr (\x xs -> (x * 10):xs) [] $ filter (\x -> x `mod` 2 == 0) $ filter (> 3) [5,9,8,3,6,7,1,5,2]

sfold.scala

// this
List(5,9,8,3,6,7,1,5,2).foldRight(Nil:List[Int])((i, xs) => if (i > 3) i::xs else xs)
                       .foldRight(Nil:List[Int])((i, xs) => if (i % 2 == 0) i::xs else xs)
                       .foldRight(Nil:List[Int])((i, xs) => (i * 10)::xs)
                       
// that
for { 
  i <- List(5,9,8,3,6,7,1,5,2)
  if (i > 3)
  if (i % 2 == 0)
} yield (i * 10)

// or
List(5,9,8,3,6,7,1,5,2).filter(_ > 3)
                       .filter(_ % 2 == 0)
                       .foldRight(Nil:List[Int])((i, xs) => (i * 10)::xs)