What is a Functor in Haskell and how do I use it?

What is a Functor in Haskell and how do I use it?

A Functor in Haskell is a type class that allows you to apply a function over wrapped values. It provides the 'fmap' function.

Can you give me an example of using fmap with a Functor?

Sure! If you have a list, you can use fmap to apply a function to each element. For example: fmap (+1) [1, 2, 3] results in [2, 3, 4].

Are there other types that are Functors?

Yes, many types are Functors, including Maybe, Either, and even custom data types you define.

How do I create a custom Functor?

To create a custom Functor, you need to implement the 'fmap' function for your data type, following the Functor type class definition.