> Sometimes the "monad patterns" will appear in a language under another name, or will be used "under the hood" to implement a particular API. Clojure/Script's `let` for example is essentially the Identity Monad; and its `for` is very much akin to the List Monad (the same is true for list comprehensions in other languages).
I knew this from reading monad tutorials. And yes, certainly there exist useful things that happen to be monads. But I question the usefulness of explicitly pointing that out and saying, "Here's a monad library. I'm going to use this monad library to build X. You can use all the normal monadic functions on X, because it's a monad", as opposed to putting the monad stuff to the side and just building X. What would you gain from building `let` or list comprehensions atop a monad library? Would it be worth the users you'd confuse? The concept of monad is far too abstract to be intuitive to most people, so there is a cognitive cost to making people think about them.
1. http://brandon.si/code/the-state-monad-a-tutorial-for-the-co...