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Comment by spankalee | Hacker News Reader

Honestly, I still don't get it. Which part is the monad? What's the example showing?

The monad is the primitive/function that represents (VALUE or NULL), or in this case (CHICKEN or BEEF or ...). In this example, the ingredients and the burrito itself are also monads.

If you type-check your Python/JS/Ruby code, monads are a functional-style solution to get rid of that code (functional programmers don't like type-checking).

That's my simplest explanation at least!

Which symbol or identifier in the code is the monad?

In the code example, it'd be `Burrito` along with the `>>=` operator and `return` function. In Haskell, Monad is the type class (more or less an Interface) that specifies the types of those functions, so anything that implements Monad is said to be "a monad". F# does not have type classes, so there's not one single thing to point to in that code as a monad, only the interface being implemented as a whole.

  type Burrito = Meat option \* Ingredient list

  let (>>=) burrito f =
    match burrito with
    | Some meat, ingredients -> f (Some meat, ingredients)
    | None, _ -> None, []

  
  let returnBurrito (meat, ingredients) = meat, ingredients

The monad is none of the identifiers. If you combine the definitions you get a type with an interface equivalent to the monad and some floof methods (like the mission burrito starter, that's there just for convenience).

type Burrito is a monad, because the functions >>= and returnBurrito are defined. Any type for which those two functions are defined is a monad.

The Burrito type is the monad.

Monads are just function chaining worshiped in the holy language of category theory.

You have an array of state, and you can call a method on it that returns a new array of state, that you can call a method on, that returns a new array of state, etc. And that concept of doing state -> function call -> state is the holy Monad.

A JS pleb would write instead:

burrito = (new Tortilla()).addMeat(Chicken).addMissionBurritoIngredients().holdThe(Cheese)

No one would be confused about what was going on, and it would be basically the same thing.

Yes. But perhaps a syntax around the type of the return object to match with the next function.

While it is just functions. To say, it's just functions all the way down, doesn't help you talk about them.

Could say that math is all functions, and having some language to discuss that subject is maybe more the purpose of the monad.

Kind of like if you were to say to a math student, just go study functions, no need for any school or language to describe what is happening.

But yes, category theory is a bit heavy handed to a programmer just needing to chain some functions.

Maybe the problem is such a vast gulf between the junior dev just needing to know how to chain some things, and the category mathematician that has never coded. Yet they are circling around the same subject.

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