Syntax example scan sheet for Haskell.

haskell_up_to_speed.hs

-- Haskell scan sheet / Cheat sheet

import System.IO
import Control.Concurrent
import qualified Data.Map as Map

-- variables and constants
integerVar :: Int
integerVar = 10

stringVar :: String
stringVar = "Hello, Haskell!"

-- functions
greet :: String -> String
greet name = "Hello " ++ name

-- recursion (loop)
count :: Int -> IO ()
count 0 = putStrLn "Finished counting"
count n = do
    putStrLn $ "Count: " ++ show n
    count (n - 1)

-- conditional statements
checkNumber :: Int -> String
checkNumber n
    | n > 5 = "Number is greater than 5"
    | n == 5 = "Number is exactly 5"
    | otherwise = "Number is less than 5"

-- data structures
numbers :: [Int]
numbers = [1, 2, 3, 4, 5]

myMap :: Map.Map String Int
myMap = Map.fromList [("a", 1), ("b", 2)]

-- error handling using maybe
safeDiv :: Int -> Int -> Maybe Int
safeDiv _ 0 = Nothing
safeDiv x y = Just (x `div` y)

-- file I/O
writeToFile :: IO ()
writeToFile = do
    let content = "Writing to a file in Haskell!"
    writeFile "example.txt" content

readFromFile :: IO ()
readFromFile = do
    content <- readFile "example.txt"
    putStrLn $ "File content: " ++ content

-- concurrency
createThread :: IO ()
createThread = do
    forkIO $ putStrLn "Running in a separate thread"
    putStrLn "This is the main thread"

main :: IO ()
main = do
    putStrLn $ greet "World"
    count 5
    putStrLn $ checkNumber integerVar
    putStrLn "Performing file operations:"
    writeToFile
    readFromFile
    createThread