cviceni2, Haskell - rextester

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--ghc 8.0.2
factorial  :: Int -> Int
factorial  0 = 1
factorial  n = n * factorial  (n-1)

factorial'  :: Int -> Int
factorial' n | n==0 = 1
             | otherwise = n * factorial'' (n-1)

factorial''  :: Int -> Int        
factorial'' n = if n==0 then 1 else n * factorial'' (n-1)

fib :: Int->Int
fib 0 = 1
fib 1 = 1
fib n = fib (n-1) + fib (n-2)

fib' :: Int -> Int
fib' n = tmp n 1 1 where
  tmp 0 a _ = a 
  tmp x a b = tmp (x-1) b (a+b)
  
leapYear :: Int -> Bool
leapYear x = x `mod` 4 == 0 && x `mod` 100 /= 0 || x `mod` 400 == 0

max3 :: Int -> Int -> Int -> Int
max3 x y z = (x `max2` y) `max2` z

combinations :: Int -> Int -> Int
combinations n k = factorial n `div` (factorial k * factorial (n-k))

combinations' :: Int -> Int -> Int
combinations' n k = fromIntegral(factorial n) `div` fromIntegral(factorial k * factorial (n-k))

numberOfRoots :: Int -> Int -> Int -> Int
numberOfRoots a b c = let d = b*b - 4 * a *c
                      in if d<0 then 0 else if d == 0 then 1 else 2
                      
gcd' :: Int -> Int -> Int
gcd' a b | a > b = gcd' (a-b) b
         | a < b = gcd' a (b-a)
         | a==b = a

gcd2 :: Int -> Int -> Int         
gcd2 a 0 = a
gcd2 a b = gcd2 b (a `mod` b)

isPrime :: Int -> Bool
isPrime 1 = False
isPrime y = isPrimeTest y (y-1) where
  isPrimeTest _ 1 = True 
  isPrimeTest n x | n `mod` x ==0 = False
                  | otherwise = isPrimeTest n (x-1)

main = do { print $ factorial 5;
            print $ fib 5;
            print $ leapYear 2000;
            print $ leapYear 2020;
            print $ leapYear 2100;
            print $ leapYear 2019;
            print $ max2 5 8;
            print $ max3 5 8 4;
            print $ combinations 8 5;
            print $ numberOfRoots 1 4 2;
            print $ gcd' 30 18;
            print $ isPrime 7;
          }

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Compilation time: 1.35 sec, absolute running time: 0.2 sec, cpu time: 0.02 sec, memory peak: 5 Mb, absolute service time: 1,7 sec