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hirrolot
metalang99
C2021–2025
hirrolot / metalang99

metalang99

Full-blown preprocessor metaprogramming

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17Mentions
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REPOSITORY AT A GLANCE

What to know before exploring

What it is

Full-blown preprocessor metaprogramming

GitHub

Where it is used

No documented product use has been verified yet.

What people are saying

The CPP does allow quite advanced metaprogramming, it's just so obtuse to use and requires insane hacks so almost nobody does. See one of my favorite projects…

lpribis used a recommendation phrase. One indexed comment matches. This is a phrase match, not a verdict.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

No other repository is repeatedly linked in the same discussions.

This week on Hacker News

Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 5:04:57 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year17 dated mentions

Observed mentions: 2021-02-04 11:27:14 UTC to 2025-11-06 08:56:45 UTC.

02468102021-01-01 00:00:00 UTC to 2022-01-01 00:00:00 UTC (exclusive): 9 mentions; 4 submissions, 5 comments20212022-01-01 00:00:00 UTC to 2023-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2023-01-01 00:00:00 UTC to 2024-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments20232024-01-01 00:00:00 UTC to 2025-01-01 00:00:00 UTC (exclusive): 1 mentions; 1 submissions, 0 comments2025-01-01 00:00:00 UTC to 2026-01-01 00:00:00 UTC (exclusive): 3 mentions; 2 submissions, 1 comments2025

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20212021-01-01 00:00:00 UTC2022-01-01 00:00:00 UTC945
20222022-01-01 00:00:00 UTC2023-01-01 00:00:00 UTC202
20232023-01-01 00:00:00 UTC2024-01-01 00:00:00 UTC202
20242024-01-01 00:00:00 UTC2025-01-01 00:00:00 UTC110
20252025-01-01 00:00:00 UTC2026-01-01 00:00:00 UTC321

What Hacker News says

17 sources
lifthrasiir·Sep 30, 2023
There are also other approaches. Macro variants making use of `__VA_ARGS__` would be probably the best trade-off. If you want a slightly more ergonomic syntax, something like Metalang99 [1] will help (and the author even wrote a post about this exact subject [2]). Codegen is another option which may work better than other options depending on the situation and exact implementation strategy. And there is always the Reflection TS [3], which may or may not be incorporated to C++26... [1] https://github.com/Hirrolot/metalang99 [2] https://hirrolot.github.io/posts/pretty-printable-enumeratio... [3] https://en.cppreference.com/w/cpp/experimental/reflect
In How to convert an enum to string in C++
CuriousCosmic·Nov 22, 2022
Honestly I have to disagree. There is nothing particularly special about what Super Template Tetris(STT) is doing. At its core, template metaprogramming is just functional programming at compile time. STT is just a template and a runtime function which do the following: 1, take an input via compile time flag (the `-D DIRECTION`) 2. take a type input from an included header file containing the current state (`#include "current_game.h"`) 3. via functional programming, compute the results of a single step of the game. 4. specialise a single function using the results of step 3. this function prints the computed result to the screen and the computed game state to a file (`./current_game.h`). 5. gcc/clang exits. compilation is complete. 6. call the compiled binary. 7. the binary runs the specialised function and prints the outputs. Sure it's f
Read the rest
ucky and you shouldn't do that in production but what sane individual is writing a piece of code that at runtime (after compiling) seeks out one of its own source files and modifies that file? To prevent this from being possible you'd have to remove runtime file IO from the language. The other potential solutions wouldn't work: 1. Remove templates entirely: Still would be possible using https://github.com/Hirrolot/metalang99 which solely uses the preprocessor. Given that the pre-processor is literally just term substitution(a glorified copy/paste engine), if you removed that as well, you'd have to accept no form of metaprogramming at all. 2. Remove the ability to #include other files: Could still be done by doing everything inline. `#include` is just copy-paste anyways so it's more an abstraction than anything else to the compiler and preprocessor, it's basically the same as if all the code was pasted into the same file. That leaves you with removing file IO. Without IO a programming language is basically useless, particularly as a systems programming language.
In Inside boost::unordered_flat_map
Hirrolot·Jul 22, 2021
> The c preprocessor replaces something by something else and the process is completely opaque. If you have multiple layers of macros, codes becomes impossible to follow, isolate and understand with a debugger or a profiler. It's not true for Datatype99 & Interface99. Their code generation semantics are completely transparent to a user of these macros [1] [2]. > That has made our codebase extremely robust. We use real metaprogramming with our own tools, not hacks, and that gives us a tremendous competitive advantage because problems takes 1/10th or 1/100th the time for being solved. If you use third-party tools and you're okay with that, I'm not saying you should stop using them, I'm saying that there is another solution with advantages over third-party tools [3]. If native macros haven't worked for your codebase, it doesn't mean they don
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't work for others. I would not say that the preprocessor is a thing to always avoid -- there are many examples why it is helpful, and even more helpful than any kind of third-party tools you can come up with. > Usually the way things work someone creates a easy C macro to automate some small thing, then a month later someone else creates another macro that uses the macro in a two layer system, then someone else creates another macro over the macros and leaves the old macros there. How third-party tools are different from native macros in this case? [1]: https://github.com/Hirrolot/datatype99#semantics [2]: https://github.com/Hirrolot/interface99#semantics [3]: https://github.com/Hirrolot/metalang99#q-why-not-third-party...
In Macros on Steroids: How pure C can benefit from metaprogramming
Hirrolot·Jul 22, 2021
There are several reasons why not to resort to third-party code generators [1]. This includes the burden of maintenance (think about the build process) and seamless integration of native macros with other code. Do you have some code to show bloated binaries with Datatype99/Interface99? The last time I checked the generated assembly code, it was nearly of the same size as hand-written code [2]. [1]: https://github.com/Hirrolot/metalang99#q-why-not-third-party... [2]: https://godbolt.org/z/ns6Ma7csd
In Macros on Steroids: How pure C can benefit from metaprogramming

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