Crosscut

Yesterday's example showed the first real use of a protocol. Especially interesting was how multi-type protocols need to be used differently from single-type traits. And I could have done this differently, by mentioning the module on the level of the function. But I didn't. I defined it above the function level, the scope of the current module.

And I did that because I think it leads to something interesting: The way I'm declaring the use of the protocol kinda looks as if I'm importing a module there. And if you think about that, isn't that what protocols could be? Generic modules, that accept the types they abstract over as parameters?

And of course, I'm not the one to invent this concept. OCaml already does it! And I think it's very neat. Having modules that can have parameters seems like a natural extension of what modules typically are in most languages. And if you can cover a new use case without having to introduce a totally new feature, then that seems like a potential win!