datalog_weighted_fact_database.hpp

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#pragma once
 
#include <cstddef>
#include <unordered_map>
 
#include "pulsatrix/datalog_atom.hpp"
#include "pulsatrix/datalog_dual_semiring.hpp"
 
namespace pulsatrix::datalog {
 
template <typename T>
using WeightedFactSet = std::unordered_map<Atom, T, AtomHash>;
 
template <typename T>
class WeightedFactDatabase {
public:
    WeightedFactDatabase() = default;
    explicit WeightedFactDatabase(WeightedFactSet<T> facts);
 
    void set(Atom fact, T weight);
 
    [[nodiscard]] bool contains(const Atom& fact) const { return facts_.find(fact) != facts_.end(); }
 
    [[nodiscard]] T weight_of(const Atom& fact, T default_weight) const {
        auto it = facts_.find(fact);
        return it == facts_.end() ? default_weight : it->second;
    }
 
    [[nodiscard]] std::size_t size() const { return facts_.size(); }
    [[nodiscard]] bool empty() const { return facts_.empty(); }
    [[nodiscard]] const WeightedFactSet<T>& facts() const { return facts_; }
 
    [[nodiscard]] bool operator==(const WeightedFactDatabase& other) const { return facts_ == other.facts_; }
    [[nodiscard]] bool operator!=(const WeightedFactDatabase& other) const { return !(*this == other); }
 
private:
    WeightedFactSet<T> facts_;
};
 
// Explicit instantiation declarations -- definitions live in datalog_weighted_fact_database.cpp,
// instantiated there for the two Value types this mission ships (bool, double) plus float for
// the real-valued semiring's stated "double/float" scope. Mirrors Mission 0's own
// declaration/definition split (datalog_rule.hpp/.cpp, datalog_fact_database.hpp/.cpp) rather
// than making this a header-only template -- deliberate, since only a closed, known set of
// Value types is ever needed (no caller in this mission instantiates an arbitrary T).
extern template class WeightedFactDatabase<bool>;
extern template class WeightedFactDatabase<double>;
extern template class WeightedFactDatabase<float>;
extern template class WeightedFactDatabase<DualNumber<double>>;
 
}  // namespace pulsatrix::datalog