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learnyouhaskell.hs
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learnyouhaskell.hs
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-- starting-out
doubleMe x = x + x
doubleUs x y = doubleMe x + doubleMe y
doubleSmallNumber x = if x > 100
then x
else x*2
doubleSmallNumber' x = (if x > 100 then x else x*2) + 1
conanO'Brien = "It's a-me, Conan O'Brien!"
boomBangs xs = [ if x < 10 then "BOOM!" else "BANG!" | x <- xs, odd x]
triangles = [ (a,b,c) | c <- [1..10], b <- [1..10], a <- [1..10] ]
rightTriangles = [ (a,b,c) | c <- [1..10], b <- [1..c], a <- [1..b], a^2 + b^2 == c^2]
rightTriangles' = [ (a,b,c) | c <- [1..10], b <- [1..c], a <- [1..b], a^2 + b^2 == c^2, a+b+c == 24]
-- types-and-typeclasses
removeNonUppercase :: [Char] -> [Char]
removeNonUppercase st = [ c | c <- st, c `elem` ['A'..'Z']]
addThree :: Int -> Int -> Int -> Int
addThree x y z = x + y + z
circumference :: Float -> Float
circumference r = 2 * pi * r
-- syntax-in-functions
sayMe :: (Integral a) => a -> String
sayMe 1 = "One!"
sayMe 2 = "Two!"
sayMe 3 = "Three!"
sayMe 4 = "Four!"
sayMe 5 = "Five!"
sayMe x = "Not between 1 and 5"
factorial :: (Integral a) => a -> a
factorial 0 = 1
factorial n = n * factorial (n - 1)
charName :: Char -> String
charName 'a' = "Albert"
charName 'b' = "Broseph"
charName 'c' = "Cecil"
addVectors :: (Num a) => (a, a) -> (a, a) -> (a, a)
addVectors (x1, y1) (x2, y2) = (x1 + x2, y1 + y2)
first :: (a, b, c) -> a
first (x, _, _) = x
second :: (a, b, c) -> b
second (_, y, _) = y
third :: (a, b, c) -> c
third (_, _, z) = z
head' :: [a] -> a
head' [] = error "Can't call head on an empty list, dummy!"
head' (x:_) = x
tell :: (Show a) => [a] -> String
tell [] = "The list is empty"
tell (x:[]) = "The list has one element: " ++ show x
tell (x:y:[]) = "The list has two elements: " ++ show x ++ " and " ++ show y
tell (x:y:_) = "This list is long. The first two elements are: " ++ show x ++ " and " ++ show y