Because arrows are functions/mappings, and everything we do in programming involves arrows, even in languages where arrows aren't used as notation.
The common formulation is that a "monad is just a monoid in the category of endofunctors", which is not saying much but with big words, and the joke lies in understanding what it's saying. Bartosz Milewski has a lecture video series on youtube that's all about explaining that joke, and I highly recommend it because it's actually a wonderful CS lecture series.
The common formulation is that a "monad is just a monoid in the category of endofunctors", which is not saying much but with big words, and the joke lies in understanding what it's saying. Bartosz Milewski has a lecture video series on youtube that's all about explaining that joke, and I highly recommend it because it's actually a wonderful CS lecture series.