datatype99 VS Cloak

Sum types and pattern matching have already been hacked together in a preprocessor macro in C; see https://github.com/Hirrolot/datatype99.

It does not. There are people who have implemented such constructs in C code however, for example: https://github.com/Hirrolot/datatype99

Nice reference but with some strange bits:

> Algebraic data types are usually represented using a heap. Because of their non-uniformity, algebraic data types are more difficult to scan.

Using a heap??? We can represent ADTs using stack as well, that's what we usually do in C and Rust.

Shameless plug: https://github.com/Hirrolot/datatype99 (a library of mine that generates type-safe ADTs for pure C99).

I agree; I would especially not recommend abusing macros throughout an application codebase too much. Conceptually, Metalang99 is more of a (sub)language than a library, which also adds some entry barrier. Ideally, I see the application of Metalang99 being used "behind the scenes", e.g., encapsulated in separate code files/libraries such as Datatype99 and Interface99. This is what I (mostly) do in SmolRTSP.

I've done something similar with Datatype99 and Interface99. They are like a macro eDSL that compiles to C. The first one features algebraic data types, the second one features interfaces.

If you need a bit more high-level constructions, you can use the Datatype99 and Interface99 libraries. The former provides polymorphism over data, the latter -- over behaviour (I am the creator of these libraries).

OP, you might find datatype99 and its sibling projects interesting, though they mostly leverage the C preprocessor without going all the way towards defining a new language.

You can use Datatype99 to represent your AST tagged union conveniently.

Compared to plain C, you have ADTs which help from day to day programming. You can bring them to C (https://github.com/Hirrolot/datatype99) but I don't know if the Linux guys would allow it.

Where cloak.h is https://github.com/pfultz2/Cloak/blob/master/cloak.h

The above macros are admitttedly very hairy. If C had a better preprocessor, but was otherwise unchanged, they could look a lot nicer.

> I never said such a thing. Would appreciate if you didn't put words in my mouth.

A normal part of dialogue is, "I'm going to repeat your point back to you in my own words, and you can either agree with my restating of it, or point out at which point I've misunderstood you". That's what I was doing. "Would appreciate if you didn't put words in my mouth" is unnecessary hostility.

> In my concrete example, given that FILE and DIR were classified as objects, to which of the so-called objects does F(const char*, FILE, DIR) belong?

Take any language which you agree is "OO". Add one new feature (if it isn't already there): functions/methods which don't belong to any class/object. Now the function you are talking about is possible in that language. Did the language thereby suddenly cease to be OO when we added that feature? Most people would disagree with "Yes". But if "No", what is the actual difference between C and that language?

> I use this pattern so much I actually wrote a little metaprogramming language that is capable of generating a lot of the boilerplate for you. Link in my bio, if anyone's interested in looking at it.

Your language [0] is an interesting idea. I've done a lot of similar stuff (not at work, I'm very rarely asked to write C code professionally, but I like mucking around with it in my personal time). My own approach to C metaprogramming involves obtuse preprocessor hacks (e.g [1]) and shell scripts that use grep/awk/sed to find macro invocations and spit out new header files as a result. Maybe your way is better.

A word of warning though – do you realise your name for your language is an anti-gay slur in several dialects of English? You might end up unintentionally upsetting some people with it.

[0] https://github.com/scallyw4g/poof

[1] https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,...

Well, mostly I use idioms from the Cloak Wiki (https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,...). It takes some time to realise them :)