What are closures in functional programming?

What are closures in functional programming?

Closures are functions that capture the lexical scope in which they were defined, allowing them to access variables from that scope even when invoked outside of it.

Can you give me an example of a closure?

Sure! Here's a simple example in JavaScript:

function makeCounter() {
    let count = 0;
    return function() {
        count++;
        return count;
    };
}

const counter = makeCounter();
console.log(counter()); // 1
console.log(counter()); // 2

In this example, the inner function forms a closure that retains access to the count variable.

Why are closures useful?

Closures are useful for data encapsulation, creating private variables, and maintaining state in asynchronous programming.

Are closures supported in all programming languages?

Not all languages support closures, but many modern languages like JavaScript, Python, and Ruby do. Some older languages may not have this feature.