stubs: Substitute undefined by error message

exercises/accumulate/src/Accumulate.hs

@@ -1,4 +1,4 @@
 module Accumulate (accumulate) where
 
 accumulate :: (a -> b) -> [a] -> [b]
-accumulate = undefined
+accumulate = error "You need to implement this function."

exercises/all-your-base/src/Base.hs

@@ -1,4 +1,4 @@
 module Base (rebase) where
 
 rebase :: Integral a => a -> a -> [a] -> Maybe [a]
-rebase inputBase outputBase inputDigits = undefined
+rebase inputBase outputBase inputDigits = error "You need to implement this function."

exercises/allergies/src/Allergies.hs

@@ -11,7 +11,7 @@ data Allergen = Eggs
               deriving (Eq)
 
 allergies :: Int -> [Allergen]
-allergies = undefined
+allergies = error "You need to implement this function."
 
 isAllergicTo :: Allergen -> Int -> Bool
-isAllergicTo = undefined
+isAllergicTo = error "You need to implement this function."

exercises/alphametics/src/Alphametics.hs

@@ -1,4 +1,4 @@
 module Alphametics (solve) where
 
 solve :: String -> Maybe [(Char, Int)]
-solve puzzle = undefined
+solve puzzle = error "You need to implement this function."

exercises/anagram/src/Anagram.hs

@@ -1,4 +1,4 @@
 module Anagram (anagramsFor) where
 
 anagramsFor :: String -> [String] -> [String]
-anagramsFor = undefined
+anagramsFor = error "You need to implement this function."

exercises/atbash-cipher/src/Atbash.hs

@@ -1,7 +1,7 @@
 module Atbash (decode, encode) where
 
 decode :: String -> String
-decode = undefined
+decode = error "You need to implement this function."
 
 encode :: String -> String
-encode = undefined
+encode = error "You need to implement this function."

exercises/bank-account/src/BankAccount.hs

@@ -9,13 +9,13 @@ module BankAccount
 data BankAccount = Dummy
 
 closeAccount :: BankAccount -> IO ()
-closeAccount = undefined
+closeAccount = error "You need to implement this function."
 
 getBalance :: BankAccount -> IO (Maybe Integer)
-getBalance = undefined
+getBalance = error "You need to implement this function."
 
 incrementBalance :: BankAccount -> Integer -> IO (Maybe Integer)
-incrementBalance = undefined
+incrementBalance = error "You need to implement this function."
 
 openAccount :: IO BankAccount
-openAccount = undefined
+openAccount = error "You need to implement this function."

exercises/binary-search-tree/src/BST.hs

@@ -13,25 +13,25 @@ module BST
 data BST a = Dummy deriving (Eq, Show)
 
 bstLeft :: BST a -> Maybe (BST a)
-bstLeft = undefined
+bstLeft = error "You need to implement this function."
 
 bstRight :: BST a -> Maybe (BST a)
-bstRight = undefined
+bstRight = error "You need to implement this function."
 
 bstValue :: BST a -> Maybe a
-bstValue = undefined
+bstValue = error "You need to implement this function."
 
 empty :: BST a
-empty = undefined
+empty = error "You need to implement this function."
 
 fromList :: Ord a => [a] -> BST a
-fromList = undefined
+fromList = error "You need to implement this function."
 
 insert :: Ord a => a -> BST a -> BST a
-insert = undefined
+insert = error "You need to implement this function."
 
 singleton :: a -> BST a
-singleton = undefined
+singleton = error "You need to implement this function."
 
 toList :: BST a -> [a]
-toList = undefined
+toList = error "You need to implement this function."

exercises/binary/src/Binary.hs

@@ -1,3 +1,3 @@
 module Binary (toDecimal) where
 
-toDecimal = undefined
+toDecimal = error "You need to implement this function."

exercises/bob/src/Bob.hs

@@ -1,4 +1,4 @@
 module Bob (responseFor) where
 
 responseFor :: String -> String
-responseFor = undefined
+responseFor = error "You need to implement this function."

exercises/bowling/src/Bowling.hs

@@ -5,5 +5,5 @@ data BowlingError = IncompleteGame
   deriving (Eq, Show)
 
 score :: [Int] -> Either BowlingError Int
-score = undefined
+score = error "You need to implement this function."
 

exercises/change/src/Change.hs

@@ -1,4 +1,4 @@
 module Change (findFewestCoins) where
 
 findFewestCoins :: Integer -> [Integer] -> Maybe [Integer]
-findFewestCoins target coins = undefined
+findFewestCoins target coins = error "You need to implement this function."

exercises/clock/src/Clock.hs

@@ -3,13 +3,13 @@ module Clock (clockHour, clockMin, fromHourMin, toString) where
 data Clock = Dummy
 
 clockHour :: Clock -> Int
-clockHour = undefined
+clockHour = error "You need to implement this function."
 
 clockMin :: Clock -> Int
-clockMin = undefined
+clockMin = error "You need to implement this function."
 
 fromHourMin :: Int -> Int -> Clock
-fromHourMin = undefined
+fromHourMin = error "You need to implement this function."
 
 toString :: Clock -> String
-toString = undefined
+toString = error "You need to implement this function."

exercises/connect/src/Connect.hs

@@ -3,4 +3,4 @@ module Connect (Mark(..), winner) where
 data Mark = Cross | Nought deriving (Eq, Show)
 
 winner :: [String] -> Maybe Mark
-winner = undefined
+winner = error "You need to implement this function."

exercises/crypto-square/src/CryptoSquare.hs

@@ -1,4 +1,4 @@
 module CryptoSquare (encode) where
 
 encode :: String -> String
-encode = undefined
+encode = error "You need to implement this function."

exercises/custom-set/src/CustomSet.hs

@@ -19,40 +19,40 @@ import Prelude hiding (null)
 data CustomSet a = Dummy deriving (Eq, Show)
 
 delete :: a -> CustomSet a -> CustomSet a
-delete = undefined
+delete = error "You need to implement this function."
 
 difference :: CustomSet a -> CustomSet a -> CustomSet a
-difference = undefined
+difference = error "You need to implement this function."
 
 empty :: CustomSet a
-empty = undefined
+empty = error "You need to implement this function."
 
 fromList :: [a] -> CustomSet a
-fromList = undefined
+fromList = error "You need to implement this function."
 
 insert :: a -> CustomSet a -> CustomSet a
-insert = undefined
+insert = error "You need to implement this function."
 
 intersection :: CustomSet a -> CustomSet a -> CustomSet a
-intersection = undefined
+intersection = error "You need to implement this function."
 
 isDisjointFrom :: CustomSet a -> CustomSet a -> Bool
-isDisjointFrom = undefined
+isDisjointFrom = error "You need to implement this function."
 
 isSubsetOf :: CustomSet a -> CustomSet a -> Bool
-isSubsetOf = undefined
+isSubsetOf = error "You need to implement this function."
 
 member :: a -> CustomSet a -> Bool
-member = undefined
+member = error "You need to implement this function."
 
 null :: CustomSet a -> Bool
-null = undefined
+null = error "You need to implement this function."
 
 size :: CustomSet a -> Int
-size = undefined
+size = error "You need to implement this function."
 
 toList :: CustomSet a -> [a]
-toList = undefined
+toList = error "You need to implement this function."
 
 union :: CustomSet a -> CustomSet a -> CustomSet a
-union = undefined
+union = error "You need to implement this function."

exercises/difference-of-squares/src/Squares.hs

@@ -1,10 +1,10 @@
 module Squares (difference, squareOfSums, sumOfSquares) where
 
 difference :: Integral a => a -> a
-difference = undefined
+difference = error "You need to implement this function."
 
 squareOfSums :: Integral a => a -> a
-squareOfSums = undefined
+squareOfSums = error "You need to implement this function."
 
 sumOfSquares :: Integral a => a -> a
-sumOfSquares = undefined
+sumOfSquares = error "You need to implement this function."

exercises/dominoes/src/Dominoes.hs

@@ -1,4 +1,4 @@
 module Dominoes (chain) where
 
 chain :: [(Int, Int)] -> Maybe [(Int, Int)]
-chain dominoes = undefined
+chain dominoes = error "You need to implement this function."

exercises/etl/src/ETL.hs

@@ -3,4 +3,4 @@ module ETL (transform) where
 import Data.Map (Map)
 
 transform :: Map a String -> Map Char a
-transform = undefined
+transform = error "You need to implement this function."

exercises/forth/src/Forth.hs

@@ -20,10 +20,10 @@ data ForthError
 data ForthState = Dummy
 
 empty :: ForthState
-empty = undefined
+empty = error "You need to implement this function."
 
 evalText :: Text -> ForthState -> Either ForthError ForthState
-evalText = undefined
+evalText = error "You need to implement this function."
 
 toList :: ForthState -> [Int]
-toList = undefined
+toList = error "You need to implement this function."

exercises/gigasecond/src/Gigasecond.hs

@@ -3,4 +3,4 @@ module Gigasecond (fromDay) where
 import Data.Time.Clock (UTCTime)
 
 fromDay :: UTCTime -> UTCTime
-fromDay = undefined
+fromDay = error "You need to implement this function."

exercises/go-counting/src/Counting.hs

@@ -10,7 +10,7 @@ data Color = Black | White deriving (Eq, Ord, Show)
 type Coord = (Int, Int)
 
 territories :: [String] -> [(Set Coord, Maybe Color)]
-territories = undefined
+territories = error "You need to implement this function."
 
 territoryFor :: [String] -> Coord -> Maybe (Set Coord, Maybe Color)
-territoryFor = undefined
+territoryFor = error "You need to implement this function."

exercises/grade-school/src/School.hs

@@ -3,13 +3,13 @@ module School (School, add, empty, grade, sorted) where
 data School = Dummy
 
 add :: Int -> String -> School -> School
-add gradeNum student school = undefined
+add gradeNum student school = error "You need to implement this function."
 
 empty :: School
-empty = undefined
+empty = error "You need to implement this function."
 
 grade :: Int -> School -> [String]
-grade gradeNum school = undefined
+grade gradeNum school = error "You need to implement this function."
 
 sorted :: School -> [(Int, [String])]
-sorted school = undefined
+sorted school = error "You need to implement this function."

exercises/grains/src/Grains.hs

@@ -1,7 +1,7 @@
 module Grains (square, total) where
 
 square :: Integer -> Maybe Integer
-square n = undefined
+square n = error "You need to implement this function."
 
 total :: Integer
-total = undefined
+total = error "You need to implement this function."

exercises/hamming/src/Hamming.hs

@@ -1,3 +1,3 @@
 module Hamming (distance) where
 
-distance = undefined
+distance = error "You need to implement this function."

exercises/hexadecimal/src/Hexadecimal.hs

@@ -1,3 +1,3 @@
 module Hexadecimal (hexToInt) where
 
-hexToInt = undefined
+hexToInt = error "You need to implement this function."

exercises/kindergarten-garden/src/Garden.hs

@@ -14,10 +14,10 @@ data Plant = Clover
            deriving (Eq, Show)
 
 defaultGarden :: String -> Map String [Plant]
-defaultGarden = undefined
+defaultGarden = error "You need to implement this function."
 
 garden :: [String] -> String -> Map String [Plant]
-garden = undefined
+garden = error "You need to implement this function."
 
 lookupPlants :: String -> Map String [Plant] -> [Plant]
-lookupPlants = undefined
+lookupPlants = error "You need to implement this function."

exercises/largest-series-product/src/Series.hs

@@ -1,4 +1,4 @@
 module Series (largestProduct) where
 
 largestProduct :: Int -> String -> Maybe Integer
-largestProduct = undefined
+largestProduct = error "You need to implement this function."

exercises/leap/src/LeapYear.hs

@@ -1,4 +1,4 @@
 module LeapYear (isLeapYear) where
 
 isLeapYear :: Integer -> Bool
-isLeapYear year = undefined
+isLeapYear year = error "You need to implement this function."

exercises/lens-person/src/Person.hs

@@ -31,13 +31,13 @@ data Address = Address { _street      :: String
                        }
 
 bornStreet :: Born -> String
-bornStreet = undefined
+bornStreet = error "You need to implement this function."
 
 setCurrentStreet :: String -> Person -> Person
-setCurrentStreet = undefined
+setCurrentStreet = error "You need to implement this function."
 
 setBirthMonth :: Int -> Person -> Person
-setBirthMonth = undefined
+setBirthMonth = error "You need to implement this function."
 
 renameStreets :: (String -> String) -> Person -> Person
-renameStreets = undefined
+renameStreets = error "You need to implement this function."

exercises/linked-list/src/Deque.hs

@@ -3,16 +3,16 @@ module Deque (Deque, mkDeque, pop, push, shift, unshift) where
 data Deque a = Dummy
 
 mkDeque :: IO (Deque a)
-mkDeque = undefined
+mkDeque = error "You need to implement this function."
 
 pop :: Deque a -> IO (Maybe a)
-pop = undefined
+pop = error "You need to implement this function."
 
 push :: Deque a -> a -> IO ()
-push = undefined
+push = error "You need to implement this function."
 
 unshift :: Deque a -> a -> IO ()
-unshift = undefined
+unshift = error "You need to implement this function."
 
 shift :: Deque a -> IO (Maybe a)
-shift = undefined
+shift = error "You need to implement this function."

exercises/list-ops/src/ListOps.hs

@@ -13,25 +13,25 @@ import Prelude hiding
   ( length, reverse, map, filter, foldr, (++), concat )
 
 foldl' :: (b -> a -> b) -> b -> [a] -> b
-foldl' = undefined
+foldl' = error "You need to implement this function."
 
 foldr :: (a -> b -> b) -> b -> [a] -> b
-foldr = undefined
+foldr = error "You need to implement this function."
 
 length :: [a] -> Int
-length = undefined
+length = error "You need to implement this function."
 
 reverse :: [a] -> [a]
-reverse = undefined
+reverse = error "You need to implement this function."
 
 map :: (a -> b) -> [a] -> [b]
-map = undefined
+map = error "You need to implement this function."
 
 filter :: (a -> Bool) -> [a] -> [a]
-filter = undefined
+filter = error "You need to implement this function."
 
 (++) :: [a] -> [a] -> [a]
-xs ++ ys = undefined
+xs ++ ys = error "You need to implement this function."
 
 concat :: [[a]] -> [a]
-concat = undefined
+concat = error "You need to implement this function."