detail.h

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#pragma once
 
#include <cstddef>
#include <string>
#include <string_view>
#include <functional>
 
namespace ph::detail
{
 
// References: 
// [1] https://www.cppstories.com/2021/heterogeneous-access-cpp20/
// [2] https://en.cppreference.com/w/cpp/container/unordered_map/find
struct HeterogeneousStringHash
{
    using is_transparent = void;
 
    [[nodiscard]]
    std::size_t operator () (const char* txt) const
    {
        return std::hash<std::string_view>{}(txt);
    }
 
    [[nodiscard]]
    std::size_t operator () (std::string_view txt) const
    {
        return std::hash<std::string_view>{}(txt);
    }
 
    [[nodiscard]]
    std::size_t operator () (const std::string& txt) const
    {
        return std::hash<std::string>{}(txt);
    }
};
 
}// end namespace ph::detail