nonnegative.hpp

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#ifndef EAGINE_VALID_IF_NONNEGATIVE_HPP
#define EAGINE_VALID_IF_NONNEGATIVE_HPP
 
#include "decl.hpp"
 
namespace eagine {
 
template <typename T>
struct valid_if_nonneg_policy {
 
    constexpr auto operator()(T value) const noexcept {
        return value >= T(0);
    }
 
    struct do_log {
        template <typename X, typename = disable_if_same_t<X, do_log>>
        constexpr do_log(X&&) noexcept {}
 
        template <typename Log>
        void operator()(Log& log, const T& v) const {
            log << "Value " << v << ", "
                << "less then zero "
                << "is invalid";
        }
    };
};
 
template <typename T>
using valid_if_nonnegative = valid_if<T, valid_if_nonneg_policy<T>>;
 
} // namespace eagine
 
#endif // EAGINE_VALID_IF_NONNEGATIVE_HPP