What are closures and how do they work in different programming languages?

What are closures and how do they work in different programming languages?

Closures are functions that capture the lexical scope in which they were defined. This means they can access variables from that scope even when called outside of it. Different languages implement closures in unique ways.

Can you give me an example of closures in JavaScript?

Sure! In JavaScript, a closure is created when a function is defined inside another function. For example:

function outerFunction() {
    let outerVariable = 'I am from outer scope!';
    function innerFunction() {
        console.log(outerVariable);
    }
    return innerFunction;
}

const myClosure = outerFunction();
myClosure(); // Outputs: I am from outer scope!

How do closures differ in Python?

In Python, closures are also created when a nested function captures the variables from its enclosing scope. Here's an example:

def outer_function():
    outer_variable = 'I am from outer scope!'
    def inner_function():
        print(outer_variable)
    return inner_function

my_closure = outer_function()
my_closure()  # Outputs: I am from outer scope!

What about closures in Ruby?

In Ruby, closures are implemented using blocks, procs, or lambdas. Here's a simple example using a proc:

def outer_function
    outer_variable = 'I am from outer scope!'
    inner_function = Proc.new { puts outer_variable }
    inner_function.call
end

outer_function()  # Outputs: I am from outer scope!