Infinite Negative Utility

What's next for Matzo?

Well, there's still some bugs, some runtime inefficiencies, and some quite frankly bad parse error messages. And in fact, there are a small number of language features I'd like to experiment with! I feel like all the big parts are there and it's eminently usable for a lot of random generation tasks, but it's definitely missing a few convenience things.

What drew me to Haskell?

The absolute biggest pull for me, when first coming to Haskell, wasn't monads or DSLs or even types. The biggest pull was the ability to reason about code symbolically and algebraically. Yeah, I know, that might sound like some pretentious nonsense. Bear with me. The idea here is that certain transformations in Haskell are always correct, which allows you to reason about code in a mechanical but powerful way.

What's this about conditions and restarts, then?

I said there was another part of my hypothesis, and to explain that I'll have to talk about Common Lisp's condition system. Let's start with exceptions and describe in fine detail how they work, because that'll help us understand how conditions differ. In a language with exceptions, you signal the existence of an error by you constructing a “thing” called an exception, which is usually a value of a specific type.

Is This Actually How You Write Factorial In Pony?

Absolutely not! That'd be ridiculous. A factorial implementation should take an unsigned integer so that factorial will be total and you don't need to worry about getting a negative number in the first place. Or, if your argument really needs to be signed, you can just return 0 for the negative cases and then guard against that happening elsewhere5.

Why Does It Matter?

I said near the beginning that structural types give you 95% of what you want from duck typing and 95% of what you want from static typing.