>>= operation is defined. Haskell’s I/O is based on Monads. factorial :: Int -> Int
factorial 0 = 1
factorial n = n * factorial (n - 1)​dayToNumber :: String -> Int
dayToNumber day = case day of
"Monday" -> 1
"Tuesday" -> 2
"Wednesday" -> 3
"Thursday" -> 4
"Friday" -> 5
"Saturday" -> 6
"Sunday" -> 7
_ -> error "Invalid day"​sumList :: [Int] -> Int
sumList [] = 0
sumList (x:xs) = x + sumList xs​`$` operator has the following type signature: `($) :: (a -> b) -> a -> b`.f $ x` is equivalent to `f x`.`$` operator is to eliminate the need for explicit parentheses when applying a function to an argument or composing functions. -- Without using $
result1 = sin (cos (sqrt 2))
-- Using $
result2 = sin $ cos $ sqrt 2​result1` and `result2` are equivalent. The `$` operator allows for a more concise and readable expression by avoiding nested parentheses.
2. The Dot Operator (Composition) :(.) :: (b -> c) -> (a -> b) -> a -> c`.(f . g) x` is equivalent to `f (g x)`. add1 :: Int -> Int
add1 x = x + 1
double :: Int -> Int
double x = x * 2
-- Without using .
result3 = double (add1 5)
-- Using .
result4 = double . add1 $ 5​result3` and `result4` are equivalent. The dot operator allows for a more elegant expression by composing the `add1` and `double` functions. `(.)` (dot), enabling a concise and declarative style of programming.map`, `filter`, and `fold` are higher-order functions that abstract common control flow patterns, making it easier to express transformations and computations over collections of values.map`, `filter`, `foldl`, `foldr`, and `zipWith`. These functions take other functions as arguments to perform operations on lists or other data structures. Higher-order functions provide a way to abstract and generalize computations, leading to more modular and reusable code. getLine`, `putStrLn`, or `readFile`, are specifically designed to handle I/O operations and return IO actions that can be executed in a controlled manner. main :: IO ()
main = do
putStrLn "Enter your name:"
name <- getLine
putStrLn ("Hello, " ++ name ++ "!")​`id` function, which has the type `a -> a`, meaning it works for any type `a`, and the list type `[]`, which can hold elements of any type.
2. Ad-hoc Polymorphism (Overloading) :`Eq` type class, which provides equality comparison (`==`) and inequality comparison (`/=`) operations, and the `Ord` type class, which provides ordering operations (`<`, `>`, `<=`, `>=`). data Bool = True | False​Maybe` type, which represents an optional value: data Maybe a = Nothing | Just a​Maybe` has two alternatives: `Nothing` represents the absence of a value, and `Just a` represents a value of type `a`. data Point = Point { x :: Double, y :: Double }​Point` is a product type with two fields: `x` and `y`. Each field represents a coordinate value.
ADTs are used in Haskell for a variety of purposes, including :foldl` and `foldr` are higher-order functions that allow you to reduce a list to a single value by applying a binary operation to the elements of the list. The key difference between `foldl` and `foldr` lies in their evaluation order and associativity.foldl` is: `foldl :: (b -> a -> b) -> b -> [a] -> b`.foldr` is: `foldr :: (a -> b -> b) -> b -> [a] -> b`.
Key Differences :foldl` and `foldr` depends on the specific use case, desired evaluation order, associativity requirements, and potential performance considerations. Control.Concurrent` module provides functions for creating and managing lightweight threads in Haskell.Control.Concurrent.STM` module provides functions and types for working with STM in Haskell.
3. Parallelism using `par` and `pseq` :par` and `pseq` combinators.Control.Parallel.Strategies` module, which offers higher-level constructs for expressing parallelism and controlling evaluation strategies.async`, `conduit`, and `pipes`, which provide additional abstractions and utilities for managing concurrent and parallel computations. Functor` type class in Haskell defines the `fmap` function, which allows applying a function to the values inside the functor.fmap` function has the type signature `fmap :: (a -> b) -> f a -> f b`, where `f` is the functor type constructor.Applicative` type class in Haskell extends the `Functor` type class and introduces the `pure` function to lift a value into an applicative functor.`(<*>)` function, called "apply," which allows applying a function inside an applicative functor to a value inside another applicative functor.(<*>)` function has the type signature `(<*>) :: f (a -> b) -> f a -> f b`.Monad` type class in Haskell defines the `return` function (equivalent to `pure`) and the `(>>=)` function (pronounced "bind"), which allows sequencing computations within a monadic context.(>>=)` has the type signature `(>>=) :: m a -> (a
-> m b) -> m b`, where `m` is the monad type constructor.do` notation, which provides a more readable syntax for composing monadic computations.