indicated.hpp

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#ifndef EAGINE_VALID_IF_INDICATED_HPP
#define EAGINE_VALID_IF_INDICATED_HPP
 
#include "decl.hpp"
 
namespace eagine {
 
template <typename Indicator, typename Comparable, Comparable Value>
struct valid_if_indicated_policy {
    Indicator _indicator{};
 
    constexpr valid_if_indicated_policy() noexcept = default;
 
    constexpr valid_if_indicated_policy(Indicator indicator) noexcept
      : _indicator(indicator) {}
 
    template <typename T>
    auto operator()(const T&) const noexcept {
        return Comparable(_indicator) == Value;
    }
 
    struct do_log {
        template <typename X>
        constexpr do_log(X) noexcept {}
 
        template <typename Log, typename T>
        void operator()(Log& log, const T&) const {
            log << "indicator is " << Value;
        }
    };
};
 
template <
  typename T,
  typename Indicator,
  typename Comparable = bool,
  Comparable Value = true>
using valid_if_indicated =
  valid_if<T, valid_if_indicated_policy<Indicator, Comparable, Value>>;
//------------------------------------------------------------------------------
} // namespace eagine
 
#endif // EAGINE_VALID_IF_INDICATED_HPP