Philip Wadler (opens in new tab)

On page 138 of the second edition of his 1971 book, "Categories for the Working Mathematician", American mathematician Saunders Mac Lane inadvertently coined one of the most famous memes ever made around programming. It is there, precisely there, and not anywhere else, where the phrase "a monad in X is just a monoid in the category of endofunctors" was published for the first time. As is often the case, the true origin of the meme got lost in collective memory, and it ended up being falsely a...