Haskell Programming Language Cheatsheet

Basic cheat sheet for Haskell. This cheatsheet covers some fundamental concepts and syntax in Haskell.

1. Basic Syntax

1.1 Declarations

-- Comments start with --
variableName = value

1.2 Functions

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

1.3 Lists

list = [1, 2, 3, 4]

1.4 Tuples

tuple = (1, "Hello")

2. Types and Typeclasses

2.1 Type Declarations

-- Explicit type declaration
add :: Int -> Int -> Int

2.2 Common Types

• Int, Integer, Float, Double, Char, Bool

2.3 Typeclasses

class Eq a where
  (==) :: a -> a -> Bool
  (/=) :: a -> a -> Bool

3. Pattern Matching

factorial :: Integer -> Integer
factorial 0 = 1
factorial n = n * factorial (n - 1)

4. Lists and List Comprehensions

4.1 Basic List Operations

-- Concatenation
combinedList = [1, 2, 3] ++ [4, 5, 6]

-- Get element by index
elementAtIndex = combinedList !! 2

-- List comparison
isGreaterThan = [1, 2, 3] > [2, 3, 4]

4.2 List Comprehensions

squares = [x^2 | x <- [1..5]]

5. Higher-Order Functions

5.1 Map

squareAll :: [Int] -> [Int]
squareAll list = map (\x -> x^2) list

5.2 Filter

evenNumbers :: [Int] -> [Int]
evenNumbers list = filter (\x -> x `mod` 2 == 0) list

6. Lambdas

multiplyByTwo = \x -> x * 2

7. Monads

7.1 Maybe Monad

safeDivide :: Float -> Float -> Maybe Float
safeDivide _ 0 = Nothing
safeDivide x y = Just (x / y)

7.2 IO Monad

main :: IO ()
main = do
  putStrLn "Hello, World!"

8. Modules

8.1 Importing Modules

import Data.List
import qualified Data.Map as Map

8.2 Creating Modules

module MyModule (function1, function2) where

9. Recursion

factorial :: Integer -> Integer
factorial 0 = 1
factorial n = n * factorial (n - 1)

10. Type Synonyms and Newtypes

10.1 Type Synonyms

type Name = String
type Age = Int

10.2 Newtypes

newtype Meter = Meter Double

Remember to refer to the Haskell documentation and other resources for more in-depth explanations and advanced features. This cheat sheet is meant as a quick reference guide for some fundamental concepts in Haskell.