haskell_exam_demo, Haskell

haskell_exam_demo

main = print $ "100"

-- 1.(a)
f a b = sum [x | (x, y) <- zip a b, x `mod` y == 0]

{--
main = do
    print $ f [6,9,2,7] [2,3,5,1]
    print $ f [6,9,2] [2,3,5,1]
    print $ f [1,2,3,4,5] [5,4,3,2,1]
    print $ f [10,20,30,40] [3,4,5,6,7]
--}
    
-- 1.(b)
g [] _ = 0
g _ [] = 0
g [x] [y] = if x `mod` y == 0 then x else 0
g (x:xs) (y:ys) = g [x] [y] + g xs ys

{--
main = do
    print $ g [6,9,2,7] [2,3,5,1]
    print $ g [6,9,2] [2,3,5,1]
    print $ g [1,2,3,4,5] [5,4,3,2,1]
    print $ g [10,20,30,40] [3,4,5,6,7]
--}

-- 2.(a)
p a 
    | intList == [] = 0
    | otherwise = maximum intList
    where intList = [read [x] :: Int | x <- a, x `elem` "0123456789"]
    
{--
main = do
    print $ p "Inf1-FP"
    print $ p "Functional"
    print $ p "1+1=2"
    print $ p "3.157/3 > 19"
--}

-- 2.(b)
q [] = 0
q [x] = if x `elem` "0123456789" then read[x] :: Int else 0
q (x:xs) = max (q [x]) (q xs)

{--
main = do
    print $ q "Inf1-FP"
    print $ q "Functional"
    print $ q "1+1=2"
    print $ q "3.157/3 > 19"
--}

-- 2.(c)
r a
    | intList == [] = 0
    | otherwise = maximum intList
    where intList = [read [x] :: Int | x <- filter (`elem` "0123456789") a]
    
{--
main = do
    print $ r "Inf1-FP"
    print $ r "Functional"
    print $ r "1+1=2"
    print $ r "3.157/3 > 19"
--}
    
-- 3.(a)
data Move =
    Go Int -- move the given distance in the current direction
    | Turn -- reverse direction
    | Dance -- dance in place, without changing direction
    deriving (Show,Eq)
    
data Command =
    Nil -- do nothing
    | Command :#: Move -- do a command followed by a move
    deriving (Show,Eq)
    
type Position = Int
data Direction = L | R deriving (Show,Eq)
type State = (Position, Direction)

--isFacingLeft L = True
--isFacingLeft R = False
reverseDirection L = R
reverseDirection R = L

state :: Move -> State -> State
state (Go x) (p, d) = if d == L then (p - x, L) else (p + x, R)
state Turn (p, d) = (p, reverseDirection d)
state Dance s = s

{--
main = do
    print $ state (Go 3) (0,R)
    print $ state (Go 3) (0,L)
    print $ state Turn (-2,L)
    print $ state Dance (4,R)
--}

-- 3.(b)
trace :: Command -> State -> [State]
trace Nil s = [s]
trace (c :#: m) s = x ++ [state m (last x)]
    where x = trace c s

{--
main = do
    print $ trace (Nil) (3,R) 
    print $ trace (Nil :#: Go 3 :#: Turn :#: Go 4) (0,L)
    print $ trace (Nil :#: Go 3 :#: Dance :#: Turn :#: Turn) (0,R)
    print $ trace (Nil :#: Go 3 :#: Turn :#: Go 2 :#: Go 1 :#: Turn :#: Go 4) (4,L)
--}

-- 3.(c)
visited :: State -> [State] -> Bool
visited (p, _) ss = p `elem` (map fst ss)

dancify :: Command -> Command
dancify Nil = Nil
dancify (c :#: Dance) = (dancify c) :#: Dance
dancify (c :#: m) 
    | visited (state m (last x)) x = (dancify c) :#: m :#: Dance
    | otherwise = (dancify c) :#: m
    where x = trace c (0,R)
    
{--
main = do
    print $ dancify Nil
    print $ dancify (Nil :#: Go 3 :#: Turn :#: Go 4)
    print $ dancify (Nil :#: Go 3 :#: Dance :#: Turn :#: Turn)
    print $ dancify (Nil :#: Go 3 :#: Turn :#: Go 2 :#: Go 1 :#: Turn :#: Go 4)
--}


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