Monoids in the Category of

Monoids in the Category of…

The meme words (“A Monad is just a Monoid in the Category of Endofunctors”) have become an annoying blot on the fringes of the Haskell universe. Learning resources don’t mention it, the core Haskell community doesn’t like it because it adds little and spooks newcomers, and it’s completely unnecessary to understand it if you just want to write Haskell code. But it is interesting, and it pops up in enough cross-language programming communities that there’s still a lot of curiosity about the meme words. I wrote an explanation on reddit recently, it became my highest-voted comment overnight, and someone said that it deserved its own blog post. This is that post.


I also wrote a blog post that aims to provide a more intuitive (albeit more hand wavy) explanation: Oh, THAT'S how a monad is a monoid! – Brandon Chinn

For anyone who doesnt quite have the math background to understand your blog post (like me :stuck_out_tongue:)