filter.hpp

 
#ifndef UFO_CONTAINER_TREE_PREDICATE_FILTER_HPP
#define UFO_CONTAINER_TREE_PREDICATE_FILTER_HPP
 
// STL
#include <type_traits>
 
namespace ufo::pred
{
template <class Predicate>
struct Filter {
    static_assert(false, "Predicate not implemented correctly.");
};
 
//
// Contains predicate
//
 
namespace detail
{
template <class, class>
struct contains_pred : std::false_type {
};
 
template <class T>
struct contains_pred<T, T> : std::true_type {
};
 
template <class, class>
struct contains_always_pred : std::false_type {
};
 
template <class T>
struct contains_always_pred<T, T> : std::true_type {
};
}  // namespace detail
 
template <class Pred, class Preds>
constexpr inline bool contains_pred_v = detail::contains_pred<Pred, Preds>::value;
 
template <class Pred, class Preds>
constexpr inline bool contains_always_pred_v =
    detail::contains_always_pred<Pred, Preds>::value;
 
//
// Predicate concept
//
 
template <class T>
concept Filterable = requires { typename Filter<T>; };
 
}  // namespace ufo::pred
 
#endif  // UFO_CONTAINER_TREE_PREDICATE_FILTER_HPP