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serge-sans-paille/frozen: a header-only, constexpr alternative to gperf for C++14 users

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Zhihao Yuan, ID lichray
The best way to predict the future is to invent it.
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On Monday, April 13th, 2026 at 1:32 PM, Robert Baumgartner via Std-Proposals <std-proposals_at_[hidden]> wrote:
> I want to solve the following problem: I have an enum type, potentially a large one like a set of actions. A subset of that enum type satisfies certain conditions that I want to check at runtime. That would look like this
> 
> if(someSet.contains(x)) {
> // do something
> }
> 
> std::unordered_set<T> does this job efficiently, but has to be initialized during run-time. This is suboptimal whenever the values are known at compile time, especially in ultra-low latency environments, where the run-time initialization adds overhead that can be avoided.
> The currently best compile solution that I am aware of is using a std::array like
> 
> inline static constexpr array mySet{a, b, c, …};
> 
> , which is O(log(n)) run-time at best for a lookup operation, but requires manual sorting for optimal performance and lacks the semantics of a set.
> 
> A combined std::static_unordered_set<T, N> merges both solutions in one, combining run-time efficiency with compile-time initialization.
> 
> 
> I'm aware of third-party solutions like `frozen`, and of `std::flat_map` (C++23) and `constexpr std::map` (C++26), which suggest the committee has appetite for this direction. I'd welcome pointers to any prior proposals I may have missed, and feedback on whether this is worth developing into a formal paper.
> 
> 
> Best regards,
> 
> 
> Robert Baumgartner
> 
> 
> My website: https://robba.github.io