Hello, When I have started my project, I use a Tuples but i would know if it is possible to create a record such C or Ocaml provide. I mean creating a structure where variables are accessible by a '.' or something like that.
Yes. Like this: data Tree a = Node { key :: Int, val :: a, left, right :: Tree a } | Nil deriving Show inorder :: Tree a -> [(Int,a)] inorder (Node {key = k, val = v, left = l, right = r}) = inorder l ++ [(k,v)] ++ inorder r inorder Nil = [] inorder' :: Tree a -> [(Int,a)] inorder' n@(Node {}) = inorder' (left n) ++ [(key n,val n)] ++ inorder' (right n) inorder' Nil = [] insert :: Tree a -> (Int,a) -> Tree a insert Nil (k,v) = Node { key = k, val = v, left = Nil, right = Nil } insert n@(Node {}) (k,v) = if k < key n then n { left = insert (left n) (k,v) } else n { right = insert (right n) (k,v) } t :: Tree String t = foldl insert Nil [(3,"three"),(1,"one"),(4,"two"),(5,"five")] Note that field access is by "key n", rather than by "n.key" as in other languages. "key" is just a function, like any other: it has type "Tree a -> Int". Records can be constructed directly, as in the Nil case of insert, or based on another record with changes specified, as in the Node case of insert. Pattern-matching can match none, some, or all of the fields, in any order. Because field names become functions, they live in the global name space. This means you can't use the same field name in two different data types - so it is usual to prefix the field name with an abbreviation of the data type name, such as data BinTree a = BinTree { btKey :: Int } But you can use the same field in multiple constructors of the *same* data type, as in: data Shape a = Point { loc :: (Int,Int) } | Square { loc :: (Int,Int), size :: Int } | Circle { loc :: (Int,Int), size :: Int } | Ellipse { loc :: (Int,Int), size :: Int, eccentricity :: Float } HTH. --KW 8-)