What are some practical examples of Haskell monads?

What are some practical examples of Haskell monads?

Haskell monads are a powerful abstraction for handling computations. Some practical examples include the Maybe monad for handling optional values, the List monad for non-deterministic computations, and the IO monad for input/output operations.

Can you explain the Maybe monad with an example?

Sure! The Maybe monad is used to represent computations that might fail. For example, consider a function that looks up a value in a map. If the key exists, it returns Just value; if not, it returns Nothing. This allows you to handle the absence of a value gracefully.

What about the List monad? How does it work?

The List monad allows you to work with non-deterministic computations. For instance, if you have a function that generates all possible combinations of two lists, using the List monad, you can easily combine them without writing nested loops.

Can you give me a code snippet for the IO monad?

Certainly! Here's a simple example using the IO monad to read a line from the user and print it back:

main :: IO ()
main = do
    putStrLn "Enter your name:"
    name <- getLine
    putStrLn ("Hello, " ++ name)