Comment by wat10000
7 hours ago
> Do you understand "flatmap"? Good, that's literally all a monad is: a flatmappable.
Awesome! Now I understand.
> Technically it's also an applicative functor
Aaaand you've lost me. This is probably why people think monads are difficult. The explanations keep involving these unfamiliar terms and act like we need to already know them to understand monads. You say it's just a flatmappable, but then it's also this other thing that gives you more?
But words like "incapsulation" or "polymorphism" or even "autoincrement" also sound unfamiliar and scary to a young kid who encounters them the first time. But the kid learns their meaning along the way, in a desire to build their own a game, or something. The feeling that one already knows a lot, sort of enough, and it'd be painful and boring to learn another abstract thing is a grown-up problem :-\
Those words need definitions, but they can both be defined using words most people know.
Casual attempts at defining Monads often just sweep a pile of confusion around a room for a while, until everything gets hidden behind whatever odd piece of furniture that is familiar to the person generating the definition. They then imagine they have cleared up the confusion, but it is still there.
Most engineers don't have too much trouble understanding things like List<T>, or Promise<T>, or even Optional<T>, which all demonstrate vividly what a monad does (except Promise in JS that auto-flattens).
A monad is a generalization of all them. It's a structure that covers values of type T, some "payload" (maybe one, like Promise, maybe many, like List, maybe even none, like List or Optional sometimes). You can ask it to do some operations on these values "inside", it's the map() operation. You can ask it to do similar thing when operation on each value produces a nested structure of the same kind, and flatten them into one level again: this is flatMap(). This is how Promises are chained. The result is again a structure of the same kind, maybe with "payload" of a different type.
This is a really simple abstraction, simpler than most GoF patterns, to my mind, and more fundamental and useful.
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I mean people need to be familiar with mathematics. In mathematics things form things without having to understand them.
For example, The natural numbers form a ring and field over normal addition and multiplication , but you don't need to know ring theory to add numbers..
People need to stop worrying about not understanding things. No one understands everything.
I get your point, but the natural numbers do not form a ring or field.
Now imagine if every single explanation of natural numbers talked about rings and fields. Nobody ever just says "they're the counting numbers starting from one." A few of them might say, "they're the counting numbers starting from one, and they form a ring and field over addition and multiplication." And I might think, I understand the first part, but I'm not sure what the second part is and it sounds important, so maybe I still don't know what natural numbers are.
I'm not worried, but it's amusing to see this person say it's so simple, and then immediately trample on it.