lab2hask

module Lab2 where

-- 1
fun1 :: Int -> [Int]
fun1 0 = []
fun1 x = fun1 (x-1) ++ (x : [])

fun2 :: Int -> [Int]
fun2 0 = []
fun2 x = fun2 (x-1) ++ (2*x-1 : [])

fun3 :: Int -> [Int]
fun3 0 = []
fun3 x = fun3 (x-1) ++ (2*x : [])

fun4 :: Int -> [Int]
fun4 0 = []
fun4 x = fun4 (x-1) ++ (x*x : [])

fac :: (Integral a) => a -> a
fac n = product [1..n]
fun5 :: Int -> [Int]
fun5 0 = []
fun5 x = fun5 (x-1) ++ (fac(x) : [])

fun6 :: Int -> [Int]
fun6 0 = []
fun6 x = fun6 (x-1) ++ (2 ^ (x - 1) : [])

treug :: Int -> Int
treug 1 = 1
treug n = n + treug (n-1)
fun7 :: Int -> [Int]
fun7 0 = []
fun7 x = fun7 (x-1) ++ (treug x : [])

piram :: Int -> Int
piram 1 = 1
piram n = treug n + piram (n-1)
fun8 :: Int -> [Int]
fun8 0 = []
fun8 x = fun8 (x-1) ++ (piram (x) : [])

-- 2
avg' :: [Double] -> Double -> Double -> Double
avg' [] n s = s/n
avg' (x:xs) n s = avg' xs (n+1) (s+x)
avg :: [Double] -> Double
avg x = avg' x 0 0

removeItem :: Int -> [Int] -> [Int]
removeItem n (x:xs) = if n == 1 then xs else x : removeItem (n-1) xs

addElem :: [Int] -> [Int] -> [Int]
addElem [] [] = []
addElem (x:xs) [] = x:xs
addElem [] (y:ys) = y:ys
addElem (x:xs) (y:ys) = (x + y) : addElem xs ys


swapEvenOdd :: [Int] -> [Int]
swapEvenOdd [] = []
swapEvenOdd [x] = [x]
swapEvenOdd (x:y:xs) = if (odd(x + y)) then y :swapEvenOdd (x : xs) else x : swapEvenOdd (y : xs)


twopow :: Integer -> Integer
twopow n = if n == 1 then 2 else if even n then twopow (div n 2) * twopow (div n 2) else twopow (div n 2) * twopow (div n 2) * 2

isOdd:: Int -> Bool
isOdd x = mod x 2 /= 0
removeOdd :: [Int] -> [Int]
removeOdd [] = []
removeOdd (x:xs) = if isOdd x then removeOdd xs else x : removeOdd xs

removeEmpty :: [String] -> [String]
removeEmpty [] = []
removeEmpty (x:xs) = if x == "" then removeEmpty xs else x : removeEmpty xs

countTrue :: [Bool] -> Int
countTrue [] = 0
countTrue (x:xs) = if x == True then 1 + countTrue xs else countTrue xs

makePositive :: [Int] -> [Int]
makePositive [] = []
makePositive (x:xs) = if x < 0 then (-x) : makePositive xs else x : makePositive xs

delete :: Char -> String -> String
delete _ "" = ""
delete x (y:ys) = if x == y then delete x ys else y : delete x ys

substitute :: Char -> Char -> String -> String
substitute _ _ "" = ""
substitute x y (z:zs) = if x == z then y : substitute x y zs else z : substitute x y zs