functional programming - Haskell- War card Game -

one of rules i'm trying program is:

when 2 players play cards of equal rank, triggers “war”. each player sets down 3 cards, , flips 1 more card. whoever wins between these last 2 flipped cards gets take cards in round, including 3 cards set down each player. if flipped cards match again, war triggered, resolved in same way.

i can implement first round of war inside code, part stuck when second round of war initiated when 2 players same card again. trouble having when second round of war initiated, 2 players put aside cards first war , whoever whens second war gets cards second war , first war. don't know understand how make war function store first round of cards, can see in otherwise dropped cards first round.

war :: ([int], [int]) -> ([int], [int]) war (x:xs,y:ys)  | head(drop 3 xs) > head(drop 3 (ys))  = (drop 4 (xs) ++ player1pot (x:xs) ++ player2pot (y:ys), drop 4 (ys))  | head(drop 3 xs) < head(drop 3 (ys))  = (drop 4 (xs), drop 4 (ys) ++ player2pot (y:ys) ++ player1pot (x:xs))  | otherwise  = war (drop 4 (xs),drop 4 (ys))  standardround :: ([int], [int]) -> ([int], [int]) standardround ([],y:ys) = ([],y:ys) standardround (x:xs,[]) = (x:xs,[]) standardround (x:xs,y:ys)  | x > y            = (xs ++ [y] ++ [x], ys)  | y > x            = (xs, ys ++ [x] ++ [y])  | otherwise        = war (x:xs,y:ys) 

you can use let ... in extract values of tuple

| otherwise = let (newxs,newys) = war (drop 4 xs, drop 4 ys) in               (take 3 xs ++ newxs, take 3 ys ++ newys) 

so can returned modified version. add dropped cards before or after, like.