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August 20, 2026 11:29
Specializing std::hash for std::set<A>/std::vector<A> with an arbitrary (possibly built-in) A is undefined behavior: the standard only allows program-defined specializations of standard templates when at least one template argument is program-defined. It also means users can transparently observe mata's hasher through e.g. std::hash<std::set<unsigned>>, even without touching mata types. Replace the std::set/std::vector specializations with mata::utils::SetHash and mata::utils::VectorHash, usable as the explicit Hash template argument of unordered containers, and update the two internal call sites (OrdVector's own std::hash specialization, and a local unordered_map in Nft::lookahead) accordingly. std::hash<std::pair<A, B>> is left as-is for now: it backs the Hash argument of several public API std::unordered_map<std::pair<State, State>, State> parameters (product maps), so removing it would require changing those public signatures. Refs #628.
Specializing std::hash for std::pair<A, B> with arbitrary (possibly built-in) A/B is undefined behavior for the same reason as std::set/ std::vector: the standard only allows program-defined specializations of standard templates when at least one template argument is program-defined. Replace the std::pair specialization with mata::utils::PairHash, usable as the explicit Hash template argument of unordered containers, and update the public API std::unordered_map<std::pair<State, State>, State> parameters (product maps) and their internal call sites accordingly. Refs #628.
…ed product maps The Cython .pxd/.pyx declarations for intersection()/plumbing::intersection() still declared product-map parameters as umap[pair[State, State], State], which no longer matches the C++ signatures after mata::utils::PairHash<State, State> became an explicit template argument. This made the generated C++ fail to compile (mismatched pointer types, and the pair key falling back to the now-removed std::hash<std::pair<A, B>> specialization). Expose mata::utils::PairHash as CPairHash in utils.pxd and pass it as the explicit Hash argument everywhere a product map crosses the Cython/C++ boundary.
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Specializing
std::hashforstd::set<A>/std::vector<A>with an arbitrary (possibly built-in)Ais undefined behavior: the standard only allows program-defined specializations of standard templates when at least one template argument is program-defined. It also means users can transparently observe mata's hasher through e.g.std::hash<std::set<unsigned>>, even without touching mata types.Replaces the
std::set/std::vectorspecializations withmata::utils::SetHashandmata::utils::VectorHash, usable as the explicit Hash template argument of unordered containers, and updates the two internal call sites (OrdVector's ownstd::hashspecialization, and a local unordered_map inNft::lookahead) accordingly.std::hash<std::pair<A, B>>is left as-is for now: it backs the Hash argument of several public APIstd::unordered_map<std::pair<State, State>, State>parameters (product maps), so removing it would require changing those public signatures.Refs #628.