cv5

-- real world haskell
-- learn haskell for greather good


class Visible a where
    toString :: a -> String
    size :: a -> Int
    size x = length(toString x) -- pro vsechny typy

instance  Visible Char where
    toString c =[c]

instance Visible Integer where
    toString x = (show x)


printt :: Visible a => a -> IO()
printt x= putStrLn (toString x)


data Expr = Num Int --strom
            | Add Expr Expr
            | Sub Expr Expr
            | Mul Expr Expr
            | Div Expr Expr
            | Var Char
            deriving (Eq)

expr1 :: Expr
expr1 = Mul(Add (Num 1) (Num 2))(Num 3) --(1+2)*3

ex2 :: Expr
ex2 = Add (Num 1) (Num 2)

evall :: Expr -> Int -- vyhodnoceni vyrazu Expr
evall (Num a) =a
evall (Add a b) =(evall a)+(evall b)
evall (Sub a b) =(evall a)-(evall b)
evall (Mul a b) =(evall a)*(evall b)
evall (Div a b) =(evall a) `div` (evall b)

showExpr1 :: Expr -> String-- doslovny vypis - nevypisuje zavorky kdyz jsou treba
showExpr1 (Num a) = show a
showExpr1 (Add a b) ="("++ (showExpr1 a) ++ "+" ++ (showExpr1 b) ++ ")"
showExpr1 (Sub a b) ="("++ (showExpr1 a) ++ "-" ++ (showExpr1 b) ++ ")"
showExpr1 (Mul a b) =(showExpr1 a) ++ "*" ++ (showExpr1 b)
showExpr1 (Div a b) =(showExpr1 a) ++ "/" ++ (showExpr1 b)

shExp :: Expr -> String
shExp x = showExpr x False

showExpr :: Expr -> Bool -> String-- pridat zavorky kdyz jen nutne
showExpr (Num a) _ = show a
showExpr (Add a b) True = "("++ (showExpr a False) ++ "+" ++ (showExpr b False) ++ ")"
showExpr (Sub a b) True = "("++ (showExpr a False) ++ "-" ++ (showExpr b False) ++ ")"
showExpr (Add a b) False= (showExpr a False) ++ "+" ++ (showExpr b False)
showExpr (Sub a b) False = (showExpr a False) ++ "-" ++ (showExpr b False)
showExpr (Mul a b) _ =(showExpr a True) ++ "*" ++ (showExpr b True)
showExpr (Div a b) _ =(showExpr a True) ++ "/" ++ (showExpr b True)

instance Show Expr where -- pridani do  Show fce
    show a=shExp a

deriv :: Expr -> Char -> Expr
deriv (Num a) _ = Num 0
deriv (Var a) y | a == y = Num 1
                | otherwise Num 0
deriv (Add a b) y = (Add (deriv a y) (deriv b y))
deriv (Sub a b) y = Sub (deriv a y) (deriv b y)
deriv (Mul a b) y = Add (Mul (deriv a y) (b)) (Mul (a) (deriv b y))
--deriv (Div a b) y =



main::IO()
main = do
    putStr "d"
    -- show (deriv expr1 'x')


--DU regex -> Aut
data ReggExpr   = Val Char
                | Iter ReggExpr
                | Dot ReggExpr ReggExpr
                | Plus ReggExpr ReggExpr
                deriving (Eq)

rel :: ReggExpr
rel = Dot (Dot (Iter(Plus (Val 'a') (Val 'b'))) (Val 'a')) (Val 'b')

data Symbol = Symbol Char
            | Epsilon
-- projdi upravit pridat expsilon prechody
-- spojit stavy + preznacit
-- spojeni prechodu
-- symboly spojit
-- poc a koncove stavy