How does Haskell perform I/O operations?

Haskell - Interview Questions

Haskell performs I/O operations using the IO monad, which provides a structured and controlled way to handle side effects and perform input/output operations. The IO monad allows you to encapsulate impure computations and separate them from the rest of the pure code.

Here's an overview of how Haskell performs I/O operations using the IO monad:

1. Type Signatures : I/O operations in Haskell are indicated by specific type signatures that involve the IO monad. For example, the type signature of `getLine` is `getLine :: IO String`, indicating that it performs an I/O operation to read a line of input and produces a value of type `String` wrapped in the IO monad.

2. I/O Actions : I/O operations are represented as values called "I/O actions" or "computations" in the IO monad. An I/O action is a description of the side-effecting computation to be performed, but it is not executed immediately.

3. Sequencing I/O Actions : Haskell allows you to sequence I/O actions using the `do` notation or monadic operators to specify the order in which actions should be performed. The `do` notation provides a convenient way to combine multiple I/O actions into a sequence while maintaining readability and clarity.

For example :

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

In the above example, the `putStrLn` and `getLine` actions are sequenced using the `do` notation. The actions are executed in the specified order, allowing the program to interact with the user by printing a prompt, reading input, and then printing a greeting.

4. Lazy Evaluation and IO Ordering : Haskell's lazy evaluation allows you to separate the description of I/O actions from their execution. I/O actions are performed only when their results are demanded, and the ordering of I/O actions is determined by the evaluation order of the expressions that use them.

* This lazy evaluation allows for flexibility in ordering and composition of I/O actions, and it helps separate pure expressions from impure I/O operations.

5. Pure and Impure Functions : Haskell promotes the separation of pure and impure code. Pure functions can be used to transform and process values obtained from I/O actions without performing any I/O themselves. This separation enhances modularity, testability, and code reuse.