Haskell Beginner Exercises with Tests
Follow-on from Haskell Exercises for Beginners
-- TOTAL marks: /66 module Exercises where import Prelude hiding (sum, length, map, filter, maximum, reverse, succ, pred) -- BEGIN Helper functions and data types -- The custom list type data List t = Nil | Cons t (List t) deriving Eq instance (Show t) => Show (List t) where show = show . toList where toList Nil = [] toList (Cons h t) = h : toList t -- the custom numeric type data Natural = Zero | Succ Natural deriving Eq one = Succ Zero two = Succ one three = Succ two instance Show Natural where show = show . toInt where toInt Zero = 0 toInt (Succ x) = 1 + toInt x -- functions over Natural that you may consider using succ :: Natural -> Natural succ = Succ pred :: Natural -> Natural pred Zero = error "bzzt. Zero has no predecessor in naturals" pred (Succ x) = x -- functions over List that you may consider using foldRight :: (a -> b -> b) -> b -> List a -> b foldRight _ b Nil = b foldRight f b (Cons h t) = f h (foldRight f b t) foldLeft :: (b -> a -> b) -> b -> List a -> b foldLeft _ b Nil = b foldLeft f b (Cons h t) = let b' = f b h in b' `seq` foldLeft f b' t reduceRight :: (a -> a -> a) -> List a -> a reduceRight _ Nil = error "bzzt. reduceRight on empty list" reduceRight f (Cons h t) = foldRight f h t reduceLeft :: (a -> a -> a) -> List a -> a reduceLeft _ Nil = error "bzzt. reduceLeft on empty list" reduceLeft f (Cons h t) = foldLeft f h t -- END Helper functions and data types -- BEGIN Exercises -- Exercise 1 -- Relative Difficulty: 1 -- Correctness: 2.0 marks -- Performance: 0.5 mark -- Elegance: 0.5 marks -- Total: 3 add :: Natural -> Natural -> Natural add = error "todo" -- Exercise 2 -- Relative Difficulty: 2 -- Correctness: 2.5 marks -- Performance: 1 mark -- Elegance: 0.5 marks -- Total: 4 sum :: List Int -> Int sum = error "todo" -- Exercise 3 -- Relative Difficulty: 2 -- Correctness: 2.5 marks -- Performance: 1 mark -- Elegance: 0.5 marks -- Total: 4 length :: List a -> Int length = error "todo" -- Exercise 4 -- Relative Difficulty: 5 -- Correctness: 4.5 marks -- Performance: 1.0 mark -- Elegance: 1.5 marks -- Total: 7 map :: (a -> b) -> List a -> List b map = error "todo" -- Exercise 5 -- Relative Difficulty: 5 -- Correctness: 4.5 marks -- Performance: 1.5 marks -- Elegance: 1 mark -- Total: 7 filter :: (a -> Bool) -> List a -> List a filter = error "todo" -- Exercise 6 -- Relative Difficulty: 5 -- Correctness: 4.5 marks -- Performance: 1.5 marks -- Elegance: 1 mark -- Total: 7 append :: List a -> List a -> List a append = error "todo" -- Exercise 7 -- Relative Difficulty: 5 -- Correctness: 4.5 marks -- Performance: 1.5 marks -- Elegance: 1 mark -- Total: 7 flatten :: List (List a) -> List a flatten = error "todo" -- Exercise 8 -- Relative Difficulty: 7 -- Correctness: 5.0 marks -- Performance: 1.5 marks -- Elegance: 1.5 mark -- Total: 8 flatMap :: List a -> (a -> List b) -> List b flatMap = error "todo" -- Exercise 9 -- Relative Difficulty: 8 -- Correctness: 3.5 marks -- Performance: 3.0 marks -- Elegance: 2.5 marks -- Total: 9 maximum :: List Int -> Int maximum = error "todo" -- Exercise 10 -- Relative Difficulty: 10 -- Correctness: 5.0 marks -- Performance: 2.5 marks -- Elegance: 2.5 marks -- Total: 10 reverse :: List a -> List a reverse = error "todo" -- END Exercises -- BEGIN Tests for Exercises main :: IO () main = let showNil = show (Nil :: List Int) results = [ -- add ("add", show (add one two) , show three), ("add", show (add Zero two) , show two), -- sum ("sum", show (sum (Cons 1 (Cons 2 (Cons 3 Nil)))) , show 6), ("sum", show (sum Nil) , show 0), -- length ("length", show (length (Cons 'a' (Cons 'b' (Cons 'c' Nil)))) , show 3), ("length", show (length Nil) , show 0), -- map ("map", show (map (+1) (Cons 1 (Cons 2 (Cons 3 Nil)))) , show (Cons 2 (Cons 3 (Cons 4 Nil)))), ("map", show (map (+1) Nil) , showNil), -- filter ("filter", show (filter even (Cons 1 (Cons 2 (Cons 3 Nil)))) , show (Cons 2 Nil)), ("filter", show (filter even Nil) , showNil), -- append ("append", show (append (Cons 1 (Cons 2 (Cons 3 Nil))) (Cons 4 Nil)) , show (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil))))), ("append", show (append (Cons 1 (Cons 2 (Cons 3 Nil))) Nil) , show (Cons 1 (Cons 2 (Cons 3 Nil)))), -- flatten ("flatten", show (flatten (Cons (Cons 1 (Cons 2 Nil)) (Cons (Cons 3 (Cons 4 Nil)) Nil))) , show (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil))))), -- flatMap ("flatMap", show (flatMap (Cons 1 (Cons 2 (Cons 3 Nil))) (\n -> Cons (n+1) (Cons (n+2) Nil))) , show (Cons 2 (Cons 3 (Cons 3 (Cons 4 (Cons 4 (Cons 5 Nil))))))), -- maximum ("maximum", show (maximum (Cons 3 (Cons 1 (Cons 2 Nil)))) , show 3), -- reverse ("reverse", show (reverse (Cons 1 (Cons 2 (Cons 3 Nil)))) , show (Cons 3 (Cons 2 (Cons 1 Nil)))) ] check (n, a, b) = do print ("=== " ++ n ++ " ===") print (if a == b then "PASS" else "FAIL Expected: " ++ b ++ " Actual: " ++ a) in mapM_ check results -- END Tests for Exercises
May 8th, 2010 at 11:46 pm
Thanks for putting this together. It was definitely very helpful, as I’m just starting to play around with Haskell.
Now it’s on to the cryptic intermediate exercises
-- TOTAL marks:    /66
 
module Exercises where
 
import Prelude hiding (sum, length, map, filter, maximum, reverse, succ, pred)
 
-- BEGIN Helper functions and data types
 
-- The custom list type
data List t = Nil 
			| Cons t (List t) deriving Eq
 
instance (Show t) => Show (List t) where
  show = show . toList
    where
    toList Nil = []
    toList (Cons h t) = h : toList t
 
-- the custom numeric type
data Natural = Zero 
			 | Succ Natural deriving Eq
one = Succ Zero
two = Succ one
three = Succ two
 
instance Show Natural where
  show = show . toInt
    where
    toInt Zero = 0
    toInt (Succ x) = 1 + toInt x
 
-- functions over Natural that you may consider using
succ :: Natural -> Natural
succ = Succ
 
pred :: Natural -> Natural
pred Zero = error "bzzt. Zero has no predecessor in naturals"
pred (Succ x) = x
 
-- functions over List that you may consider using
foldRight :: (a -> b -> b) -> b -> List a -> b
foldRight _ b Nil = b
foldRight f b (Cons h t) = f h (foldRight f b t)
 
foldLeft :: (b -> a -> b) -> b -> List a -> b
foldLeft _ b Nil = b
foldLeft f b (Cons h t) = let b' = f b h in b' `seq` foldLeft f b' t
 
reduceRight :: (a -> a -> a) -> List a -> a
reduceRight _ Nil = error "bzzt. reduceRight on empty list"
reduceRight f (Cons h t) = foldRight f h t
 
reduceLeft :: (a -> a -> a) -> List a -> a
reduceLeft _ Nil = error "bzzt. reduceLeft on empty list"
reduceLeft f (Cons h t) = foldLeft f h t
 
-- END Helper functions and data types
 
-- BEGIN Exercises
 
-- Exercise 1
-- Relative Difficulty: 1
-- Correctness: 2.0 marks
-- Performance: 0.5 mark
-- Elegance: 0.5 marks
-- Total: 3
add 			:: Natural -> Natural -> Natural
add x Zero		= x
add x y 		= succ (add x (pred y))
 
-- Exercise 2
-- Relative Difficulty: 2
-- Correctness: 2.5 marks
-- Performance: 1 mark
-- Elegance: 0.5 marks
-- Total: 4
sum 			:: List Int -> Int
sum 			= foldRight (+) 0 
 
-- Exercise 3
-- Relative Difficulty: 2
-- Correctness: 2.5 marks
-- Performance: 1 mark
-- Elegance: 0.5 marks
-- Total: 4
length 			:: List a -> Int
length 			= foldRight (\_ y -> 1 + y) 0
 
-- Exercise 4
-- Relative Difficulty: 5
-- Correctness: 4.5 marks
-- Performance: 1.0 mark
-- Elegance: 1.5 marks
-- Total: 7
map 			:: (a -> b) -> List a -> List b
map f			= foldRight (\x y -> Cons (f x) y) Nil
 
-- Exercise 5
-- Relative Difficulty: 5
-- Correctness: 4.5 marks
-- Performance: 1.5 marks
-- Elegance: 1 mark
-- Total: 7
filter 			:: (a -> Bool) -> List a -> List a
filter p		= foldRight (\x y -> if p x 
								     then Cons x y 
								     else y
								     ) Nil
 
-- Exercise 6
-- Relative Difficulty: 5
-- Correctness: 4.5 marks
-- Performance: 1.5 marks
-- Elegance: 1 mark
-- Total: 7
append 			:: List a -> List a -> List a
append xs ys 	= foldRight Cons ys xs


-- Exercise 7
-- Relative Difficulty: 5
-- Correctness: 4.5 marks
-- Performance: 1.5 marks
-- Elegance: 1 mark
-- Total: 7
flatten 		:: List (List a) -> List a
flatten 		= foldRight append Nil
 
-- Exercise 8
-- Relative Difficulty: 7
-- Correctness: 5.0 marks
-- Performance: 1.5 marks
-- Elegance: 1.5 mark
-- Total: 8
flatMap 		:: List a -> (a -> List b) -> List b
flatMap xs f 	= flatten (map f xs)
 
-- Exercise 9
-- Relative Difficulty: 8
-- Correctness: 3.5 marks
-- Performance: 3.0 marks
-- Elegance: 2.5 marks
-- Total: 9
maximum 		:: List Int -> Int
maximum 		= reduceRight max
 
-- Exercise 10
-- Relative Difficulty: 10
-- Correctness: 5.0 marks
-- Performance: 2.5 marks
-- Elegance: 2.5 marks
-- Total: 10
reverse 		:: List a -> List a
reverse 		= foldLeft (\x y -> Cons y x) Nil
 
-- END Exercises
 
-- BEGIN Tests for Exercises
 
main :: IO ()
main =
  let showNil = show (Nil :: List Int)
      results =
        [
        -- add
        ("add",
         show (add one two)
       , show three),
 
        ("add",
         show (add Zero two)
       , show two),
 
        -- sum
        ("sum",
         show (sum (Cons 1 (Cons 2 (Cons 3 Nil))))
       , show 6),
 
        ("sum",
         show (sum Nil)
       , show 0),
 
        -- length
        ("length",
         show (length (Cons 'a' (Cons 'b' (Cons 'c' Nil))))
       , show 3),
 
        ("length",
         show (length Nil)
       , show 0),
 
        -- map
        ("map",
         show (map (+1) (Cons 1 (Cons 2 (Cons 3 Nil))))
       , show (Cons 2 (Cons 3 (Cons 4 Nil)))),
 
        ("map",
         show (map (+1) Nil)
       , showNil),
 
        -- filter
        ("filter",
         show (filter even (Cons 1 (Cons 2 (Cons 3 Nil))))
       , show (Cons 2 Nil)),
 
        ("filter",
         show (filter even Nil)
       , showNil),
 
        -- append
        ("append",
         show (append (Cons 1 (Cons 2 (Cons 3 Nil))) (Cons 4 Nil))
       , show (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil))))),
 
        ("append",
         show (append (Cons 1 (Cons 2 (Cons 3 Nil))) Nil)
       , show (Cons 1 (Cons 2 (Cons 3 Nil)))),
 
        -- flatten
        ("flatten",
         show (flatten (Cons (Cons 1 (Cons 2 Nil)) (Cons (Cons 3 (Cons 4 Nil)) Nil)))
       , show (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil))))),
 
        -- flatMap
        ("flatMap",
         show (flatMap (Cons 1 (Cons 2 (Cons 3 Nil))) (\n -> Cons (n+1) (Cons (n+2) Nil)))
       , show (Cons 2 (Cons 3 (Cons 3 (Cons 4 (Cons 4 (Cons 5 Nil))))))),
 
        -- maximum
        ("maximum",
         show (maximum (Cons 3 (Cons 1 (Cons 2 Nil))))
       , show 3),
 
        -- reverse
        ("reverse",
         show (reverse (Cons 1 (Cons 2 (Cons 3 Nil))))
       , show (Cons 3 (Cons 2 (Cons 1 Nil))))
        ]
      check (n, a, b) = do print ("=== " ++ n ++ " ===")
                           print (if a == b then "PASS" else "FAIL Expected: " ++ b ++ " Actual: " ++ a)
 
  in mapM_ check results
 
-- END Tests for Exercises
September 3rd, 2010 at 11:22 pm
Oh, and that was solely the exercises, in a base64 encoded gzip file.