[h0l0cube]

I’m not the GP, but already Elixir can already accomplish compile time text processing with metaprogramming (like it does for inline html templating for ‘heex’ functions and files) and it’s not a huge stretch for it to be able to call a JSON parser on any string knowable at compile time and convert it into a type. That it hasn’t been done yet is probably because no one has deemed to worthwhile to implement. It does sounds cool though.

Metaprogramming is also why generics aren’t really needed in Elixir or Erlang. All specializations boil down to their reified types using macros

[Vaguely2178]

> I’m not the GP, but already Elixir can already accomplish compile time text processing with metaprogramming (like it does for inline html templating for ‘heex’ functions and files)

It's not the compile time text processing that's interesting, it's the fact that this compile time code can yield incredibly detailed types, and the fact that it's all done purely using type annotations. Almost every language that's used to build websites has some sort of server side templating language where you can sprinkle some code into your html templates.

> That it hasn’t been done yet is probably because no one has deemed to worthwhile to implement.

Maybe, or maybe it's less feasible without an advanced type system. The final version of the JSON example we're talking about ended up being 61 lines of code. Without some concrete Elixir code to inspect, this conversation is becoming very abstract.

Honestly even if some of this were possible with metaprogramming, my intuition is that it would be much more verbose and complex. I feel like if I tried to implement all of the features of TypeScript by mucking around with an abstract syntax tree using metaprogramming, I would end up with a difficult to maintain crude approximation of the real thing. I don't think we're giving compiler developers enough credit by saying everything they've worked on can be replaced with a quick macro. José Valim's blog post on static typing ended with an announcement that they've sponsored a PhD student to work on these problems.

After two days of discussion, I think we're reaching a bit of an impasse. Honestly just use what works for you!

[h0l0cube]

> It's not the compile time text processing that's interesting

You've talked right past me. Metaprogramming is not compile time text processing.

> Honestly even if some of this were possible with metaprogramming, my intuition is that it would be much more verbose and complex.

No. It's probably even how the Microsoft team are achieving the typing you're talking about. The special sauce here isn't as special as you think.

> I think we're reaching a bit of an impasse

Not really. I was just saying that what you're talking about is totally possible with metaprogramming. Not making some rhetorical play.

> José Valim's blog post on static typing ended with an announcement that they've sponsored a PhD student to work on these problems.

That's specifically because strict static typing with guards^ is at least difficult, but maybe impossible, and that's what the PhDs are trying to figure out. However, dialyzer isn't as hobbled as you imagine/purport it to be – the crux of my counterargument – and actual experience trumps speculation or casual reading on the topic.

FYI, guards and pattern matching are one of the reasons why Elixir is so damn expressive, and this kind of function typing isn't available/possible in most non-functional languages

^ https://hexdocs.pm/elixir/guards.html

[Vaguely2178]

> You've talked right past me. Metaprogramming is not compile time text processing.

I'm not talking past you. I never said metaprogramming is compile time text processing. You said "Elixir can already accomplish compile time text processing with metaprogramming", and I was just pointing out that the text processing itself is not the most interesting part of the example, it's the resultant types.

> No. It's probably even how the Microsoft team are achieving the typing you're talking about. The special sauce here isn't as special as you think.

But I don't have to reimplement any of this, because Microsoft has already written it. With enough time maybe you could implement dependent typing using metaprogramming for example, but would you then say that Elixir is just as good at dependent typing as Idris, which has that feature built in?

> I was just saying that what you're talking about is totally possible with metaprogramming.

You've graduated from saying "I think someone more savvy with Elixir would know more." to "totally possible"[1]. This does not sound like an argument from experience.

> That's specifically because strict static typing with guards^ is at least difficult, but maybe impossible, and that's what the PhDs are trying to figure out.

A lot of what you're talking about has already been implemented in other languages. This is not untrodden ground. There's no syntactic sugar for guards in JS (which TS just adds type annotations to), but semantically it's very similar to type narrowing in TS [2], which I use daily. This is not something I've read about casually on the internet.

[1] https://news.ycombinator.com/item?id=35944988

[2]https://www.typescriptlang.org/docs/handbook/2/narrowing.htm...

[h0l0cube]

> This is not something I've read about casually on the internet

Was speaking specifically about your opinions on Dialyzer and Elixir. It's very much a cursory Google around and having stronger opinions about the limits of a language than people who spend time with the language.

> You've graduated from saying "I think someone more savvy with Elixir would know more."

It took further reflection on the idea. It helps to start with at least some epistemic humility, once again the crux of this thread. I'm willing to revert to, "It ought to be possible" given that macros boil down to the final generated code (including typespecs) which is then analyzed by Dialyzer

> Elixir is just as good at dependent typing as Idris, which has that feature built in?

Metaprogramming allows features to become 'built in'. e.g., being able to integrate type checking and compiler errors for HTML/XML or other DSLs.

https://hexdocs.pm/eex/EEx.html#function_from_string/5 https://hexdocs.pm/phoenix_live_view/0.17.0/Phoenix.LiveView...

[Vaguely2178]

> Was speaking specifically about your opinions on Dialyzer and Elixir. It's very much a cursory Google around and having stronger opinions about the limits of a language than people who spend time with the language.

I think your experience with Elixir and Dialyzer (or perhaps emotional attachment to these tools) is blinding you to the fact that there are features that your favorite language lacks. I gave you a concrete example of something that's a research topic in Elixir (inferring types from guards), which has an existent analogue in TS (type narrowing). You completely ignored that and fixated on the one sentence about experience. Your entire argument is that I should defer to your authority on the topic as an anonymous commenter, because you're supposedly very experienced. It feels like a very hollow appeal to authority.

> It took further reflection on the idea.

But by your standards simple reflection is not enough to establish authority on a topic. You need to have deep personal experience with using macros to parse text before you're qualified to make a firm judgement. You event went so far as to speculate on how TypeScript implements type checking and claimed that the "secret sauce" is probably metaprogramming, despite having never worked on the compiler. This all feels incredibly contradictory.

> Metaprogramming allows features to become 'built in'. e.g., being able to integrate type checking and compiler errors for HTML/XML or other DSLs.

Built in does not mean "I might hypothetically be able to write my own macro that does this". It means it already exists in the language today.

Honestly this discussion feels like it's devolved into repetitive bickering, which is why I let your original comment about metaprogramming stand unanswered, and you reacted by following me into a different comment thread to reiterate the point.

[h0l0cube]

> emotional attachment to these tools

You've really misjudged me. I've been programming professionally for 20 years, I have used and still use a variety of languages including Typescript.

> Your entire argument is that I should defer to your authority

Never made such an argument. My argument is that you have less authority on the subject matter than someone who has spent years with the language.

> I gave you a concrete example of something that's a research topic in Elixir (inferring types from guards), which has an existent analogue in TS (type narrowing)

At best a subset of functionality than an analogue. This kind of research is being conducted by experts in type theory outside of Elixir. If it's a problem for Elixir, it's a problem for any other language that would attempt it, and absolutely I would defer to the authority of those experts who have spent years looking at type theory.

> despite having never worked on the compiler

Knowledge of meta-programming doesn't require the same skillset as writing a compiler. I'm certain you or any other capable software engineer, would be able to write a macro that parsed JSON, interrogated the typing of that JSON, and spat out a typespec with some knowledge of Elixir `defmacro`, `quote`, and `unquote`.

> Built in does not mean "I might hypothetically be able to write my own macro that does this".

Never made such a claim. My claim is that the JSON typing mechanism isn't really something that's dependent on the Typescript language and toolchain. As with my link on my last post of inline heex components, it's possible to take a text representation of something in Elixir and transform it into something that's available to the compiler (and hence also available to Dialyzer).

> bickering

Trust me there is no spite from my end.