Basic Syntax

-- Function definition
add :: Int -> Int -> Int
add x y = x + y

-- List operations
numbers = [1, 2, 3, 4, 5]
doubled = map (*2) numbers
evens = filter even numbers

-- Pattern matching
factorial :: Int -> Int
factorial 0 = 1
factorial n = n * factorial (n - 1)

-- List comprehension
squares = [x^2 | x <- [1..10]]

-- Higher-order functions
applyTwice :: (a -> a) -> a -> a
applyTwice f x = f (f x)

Type System

Monads

-- Maybe monad
safeDiv :: Double -> Double -> Maybe Double
safeDiv _ 0 = Nothing
safeDiv x y = Just (x / y)

result = do
    a <- safeDiv 10 2
    b <- safeDiv a 2
    return (b + 1)

-- IO monad
main :: IO ()
main = do
    putStrLn "What is your name?"
    name <- getLine
    putStrLn ("Hello, " ++ name)

Best Practices

• Everything is immutable by default
• Use pattern matching extensively
• Leverage lazy evaluation
• Understand monads for IO and state