What are the differences between functors and decorators in programming?

What are the differences between functors and decorators in programming?

Functors are objects that can be treated like functions, allowing you to apply them to values. Decorators, on the other hand, are a design pattern used to add behavior to functions or methods without modifying their structure.

Can you give me an example of a functor?

Sure! In JavaScript, a functor can be represented as an object with a map method. For example:

const functor = {
  value: 5,
  map: function(fn) {
    return fn(this.value);
  }
};

const result = functor.map(x => x * 2); // result is 10

And how about a decorator example?

Certainly! In Python, a simple decorator can be defined as follows:

def my_decorator(func):
    def wrapper():
        print('Something is happening before the function is called.')
        func()
        print('Something is happening after the function is called.')
    return wrapper

@my_decorator
def say_hello():
    print('Hello!')

say_hello()  # This will show messages before and after 'Hello!'

What are the main use cases for each?

Functors are often used in functional programming to handle data transformations, while decorators are commonly used in Python for logging, access control, and modifying function behavior.