[tombert]

No, it really isn’t that different. If I had a dynamic type system I would have to null check everything. If I have declare everything as a Maybe, I would have to null check everything.

For things that are invariants, that’s also trivial to check against with `if(!isValid(obj)) throw Error`.

[dwb]

Sure. The difference is that with a strong typing system, the compiler makes sure you write those checks. I know you know this, but that’s the confusion in this thread. For me too, I find static type systems give a lot more assurance in this way. Of course it breaks down if you assume the wrong type for the data coming in, but that’s unavoidable. At least you can contain the problem and ensure good error reports.

[eyelidlessness]

The point of a type system isn’t ever that you don’t have to check the things that make a value represent the type you intend to assign it. The point is to encode precisely the things that you need to be true for that assignment to succeed correctly. If everything is in fact modeled as an Option, then yes you have to check each thing for Some before accessing its value.

The type is a way to communicate (to the compiler, to other devs, to future you) that those are the expected invariants.

The check for invariants is trivial as you say. The value of types is in expressing what those invariants are in the first place.

[the-grump]

You missed the entire point of the strong static typing.

[tombert]

I don’t think I did. I am one of the very few people who have had paying jobs doing Scala, Haskell, and F#. I have also had paying jobs doing Clojure and Erlang: dynamic languages commonly used for distributed apps.

I like HM type systems a lot. I’ve given talks on type systems, I was working on trying to extend type systems to deal with these particular problems in grad school. This isn’t meant to a statements on types entirely. I am arguing that most systems don’t encode for a lot of uncertainty that you find when going over the network.

[instig007]

You're conflating types with the encoding/decoding problem. Maybe your paying jobs didn't provide you with enough room to distinguish between these two problems. Types can be encoded optimally with a minimally-required bits representation (for instance: https://hackage.haskell.org/package/flat), or they can be encoded redundantly with all default/recovery/omission information, and what you actually do with that encoding on the wire in a distributed system with or without versioning is up to you and it doesn't depend on the specific type system of your language, but the strong type system offers you unmatched precision both at program boundaries where encoding happens, and in business logic. Once you've got that `Maybe a` you can (<$>) in exactly one place at the program's boundary, and then proceed as if your data has always been provided without omission. And then you can combine (<$>) with `Alternative f` to deal with your distributed systems' silly payloads in a versioned manner. What's your dynamic language's null-checking equivalent for it?

[the-grump]

With all due respect, you can use all of those languages and their type systems without recognizing their value.

For ensuring bits don't get lost, you use protocols like TCP. For ensuring they don't silently flip on you, you use ECC.

Complaining that static types don't guard you against lost packets and bit flips is missing the point.

[tombert]

With all due respect, you really do not understand these protocols if you think “just use TCP and ECC” addresses my complaints.

Again, it’s not that I have an issue with static types “not protecting you”, I am saying that you have to encode for this uncertainty regardless of the language you use. The way you typically encode for that uncertainty is to use an algebraic data type like Maybe or Optional. Checking against a Maybe for every field ends up being the same checks you would be doing with a dynamic language.

I don’t really feel the need to list out my full resume, but I do think it is very likely that I understand type systems better than you do.

[the-grump]

Fair enough, though I feel so entirely differently that your position baffles me.

Gleam is still new to me, but my experience writing parsers in Haskell and handling error cases succinctly through functors was such a pleasant departure from my experiences in languages that lack typeclasses, higher-kinded types, and the abstractions they allow.

The program flowed happily through my Eithers until it encountered an error, at which point that was raised with a nice summary.

Part of that was GHC extensions though they could easily be translated into boilerplate, and that only had to be done once per class.

Gleam will likely never live to that level of programmer joy; what excites me is that it’s trying to bring some of it to BEAM.

It’s more than likely your knowledge of type systems far exceeds mine—I’m frankly not the theory type. My love for them comes from having written code both ways, in C, Python, Lisp, and Haskell. Haskell’s types were such a boon, and it’s not the HM inference at all.

[folex]

> ends up being the same checks you would be doing with a dynamic language

Sure thing. Unless dev forgets to do (some of) these checks, or some code downstream changes and upstream checks become gibberish or insufficient.

[tombert]

I know everyone says that this is a huge issue, and I am sure you can point to an example, but I haven’t found that types prevented a lot of issues like this any better than something like Erlang’s assertion-based system.