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Show HN: CXXStateTree – A modern C++ library for hierarchical state machines

(github.com)
48 points zigrazor | 3 comments | 07 Jul 25 06:06 UTC | HN request time: 0.473s | source

Hi HN!

I've built [CXXStateTree](https://github.com/ZigRazor/CXXStateTree), a modern C++ header-only library to create hierarchical state machines with clean, intuitive APIs.

It supports: - Deeply nested states - Entry/exit handlers - State transitions with guards and actions - Asynchronous transitions with `co_await` (C++20 coroutines) - Optional runtime type identification for flexibility

It's ideal for complex control logic, embedded systems, games, robotics, and anywhere you'd use a finite state machine.

I’d love feedback, use cases, or contributions from the community!

Repo: https://github.com/ZigRazor/CXXStateTree

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dgan ◴[10 Jul 25 18:22 UTC] No.44523973[source]▶
i am by no means a C++ expert, but isn't "pragma once" frowned upon?
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kookamamie ◴[10 Jul 25 18:29 UTC] No.44524039[source]▶
No, it is the way. Edit: no one has time for inventing unique names for include guards.
replies(2): >>44524438 #>>44524781 #
hdhdjd ◴[10 Jul 25 19:10 UTC] No.44524438[source]▶
Does anyone write those by hand anyway in any kind of project the size where it would matter?

#pragma once is broken by design

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bogwog ◴[10 Jul 25 19:25 UTC] No.44524590[source]▶
I don't understand what you're saying here. #pragma once does the job that include guards used to do, but with less work, and in a less error prone way. How is it broken, and how is the size of a project relevant?
replies(1): >>44524820 #
1. motorest ◴[10 Jul 25 19:55 UTC] No.44524820[source]▶
> I don't understand what you're saying here. #pragma once does the job that include guards used to do, (...)

They don't. They are not C++ and at most they are compiler-specific.

It's fine if you opt to not write C++ and instead target specific compilers instead. Just don't pretend it's not frowned upon or kosher.

replies(2): >>44524966 #>>44526854 #
2. bogwog ◴[10 Jul 25 20:09 UTC] No.44524966[source]▶
TIL about the existence of a passionate #pragma once hating subculture.

Since you seem to be more knowledgeble about this, I'm curious to know which C++ compilers lack support? I know that at least the 3 big ones do (GCC, Clang, and MSVC) and they have for a very long time.

3. jcelerier ◴[10 Jul 25 23:28 UTC] No.44526854[source]▶
it's absolutely not frowned upon in 2025. All the compilers that matter (GCC, Clang and MSVC) support and have supported them for two decades. Major projects use #pragma once internally - I see files using it in Qt, LLVM, etc.