62 lines
1.6 KiB
Haskell
62 lines
1.6 KiB
Haskell
{- types.hs
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This file contains some of the examples on types to be shown in the
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second class of the course "Haskell for Life", by Sergiu Ivanov
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(sivanov@lacl.fr):
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http://lacl.fr/~sivanov/doku.php?id=en:haskell_for_life
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This file is distributed under the Creative Commons Attribution Alone
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licence.-}
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data BookInfo = Book Int String [String]
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deriving (Show)
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data Coordinates = Cartesian2D Double Double | Polar2D Double Double
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deriving (Show)
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printCoordinate :: Coordinates -> String
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printCoordinate (Cartesian2D x y) = "x=" ++ show x ++ ",y=" ++ show y
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printCoordinate (Polar2D ρ φ) = "ρ=" ++ show ρ ++ ",φ=" ++ show φ
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data Pair a = Pair a a
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deriving (Show)
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-- | Returns 'True' if the given 'Maybe' contains 'Nothing'.
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myIsNothing :: Maybe a -> Bool
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myIsNothing Nothing = True
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myIsNothing (Just _) = False
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-- | Extracts the contents of a 'Maybe' (unpacks it).
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myFromJust :: Maybe a -> a
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myFromJust (Just x) = x
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data List a = Cons a (List a) | Nil
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deriving (Show)
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-- | Converts an instance of 'List' to a normal Haskell list.
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fromMyList :: List a -> [a]
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fromMyList (Cons x xs) = x:fromMyList xs
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fromMyList Nil = []
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-- | Converts a normal Haskell list to an instance of 'List'.
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toMyList :: [a] -> List a
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toMyList (x:xs) = Cons x (toMyList xs)
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toMyList [] = Nil
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data FunnyList a = a :/ (FunnyList a) | Void
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deriving Show
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data Tree a = Node a (Tree a) (Tree a) | Empty
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deriving (Show, Read)
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-- | Returns a list of the values contained in the leaves of a tree.
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fruit :: Tree a -> [a]
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fruit Empty = []
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fruit (Node x Empty Empty) = [x]
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fruit (Node _ l r) = fruit l ++ fruit r
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