Peaker on Roy — small functional language that compiles to JavaScript

Comment on Roy — small functional language that compiles to JavaScript parent

That's actually not a Monad :-)

To be a monad, return must be a left and right identity:

    x >>= return = x
    return x >>= f = f x

By having return do things other than wrapping the value, the monad laws are broken.

Similarly, bind cannot have such effects, it would break its associativity.

joebo 14y

The option monad example might be closer. I'm having trouble figuring out how to get the value out of it though

       data Option a =
	  Some a | None

        let optionMonad = {
		return: fn x =
		Some x
	  bind: fn x f = match x
		case (Some a) = f a
		case None = None
	}

	let m = (do optionMonad
	  bind x = Some 1
	  let y = 2
	  bind z = Some 3
	  return x + y + z
	)

	match m 
		case (Some x) = console.log x

shows an error Error: Type error: Native is not Option 'dwk

pufuwozu 14y

Bug in the type system. Fixed. Roy could be cached so you might need to force a refresh.

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