Caltech CS 11 Haskell Track Lab 1

lab1.hs

add_and_double :: Double -> Double -> Double
add_and_double x y = (x + y) * 2

(+*) :: Double -> Double -> Double
(+*) x y = x `add_and_double` y

solve_quadratic_equation :: Double -> Double -> Double -> (Double, Double)
solve_quadratic_equation a b c = (x1, x2)
  where disc = sqrt (b ** 2 - 4 * a * c)
        x1 = (disc - b) / (2 * a)
        x2 = (-1) * (disc + b) / (2 * a)

first_n :: Int -> [Int]
first_n n = take n [1..]

first_n_integers :: Integer -> [Integer]
first_n_integers n | n < 0 = error "foobar"
                   | otherwise =
                     let take_integer m xs | m < 0 = error "take_integer: m must be non-negative"
                                           | m == 0 = []
                                           | xs == [] = error "take_integer: not enough items in list"
                                           | otherwise = head xs : take_integer (m - 1) (tail xs)
                     in take_integer n [1..]

f :: Integer -> Integer
f n | m > 0 = 5
    | otherwise = 2
  where m = n * n

double_factorial :: Integer -> Integer
double_factorial n | n <= 1 = 1
                   | otherwise = factorial n * double_factorial (n - 1)
    where factorial m | m <= 1 = 1
                      | otherwise = m * factorial (m - 1)

factorials :: [Integer]
factorials = 1 : 1 : zipWith (*) (tail factorials) [2..]