Yes, this article is doing a bad job at explaining why you would want effects, and one of the main advantages is exactly that it becomes part of the type system, essentially coloring every single function with a set of effects it needs to be called. As the article used JavaScript it shows what untyped effects would look like, which in my opinion is awful. If you want to use algebraic effects today, I highly recommend Unison. If you’re on the JVM, Flix is doing major advances with effects!

https://www.unison-lang.org/

https://flix.dev/

When you need to use an effect, you need it in the type. If you directly call a function using some other effect, it propagates into your function. So far, so colourful.

But you can have generic effects. Your arguments and return type can specify "any effect", indicating your function can use a type with any effect safely, or can be used in any effect context safely.

Passing an async value to a function doesn't mean that function must now also be an async function. It can be a "for all effects, do the thing" function. The code duplication problem is gone.

No, they are function colouring. That's the point.

Someone writes a post lamenting red and blue functions, and everyone eats it up.

Substitute colour for something meaningful and the idea becomes idiotic.

"Top level function declares that it is non-blocking, but when I try to call a small blocking function from it, I have to change the declaration to blocking???"

Yes, yes you do.

Total functions can't call non-total functions.

Deterministic functions can't call nondeterministic functions.

Non-IO functions can't call IO functions.