What is the point of using Monad in a program?

Question

Say I'm creating an image processing library using Haskell. I have defined several of my own data types.

When should I declare some of my data types as Monad (or functor or application functor, etc.)? And what is the use of this?

I understand that if some data types can be "mapped", I can declare it an instance of a functor. But if I do so, then what is the use?

This may be a really stupid question, but I'm still trying to get into the field of functional programming.

Answer 1

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