--- /dev/null
+#pragma once
+
+#include <boost/variant/static_visitor.hpp>
+
+#include "mstch/mstch.hpp"
+
+namespace mstch {
+
+class has_token: public boost::static_visitor<bool> {
+ public:
+ has_token(const std::string& token): m_token(token) {
+ }
+
+ template<class T>
+ bool operator()(const T&) const {
+ return m_token == ".";
+ }
+
+ bool operator()(const map& map) const {
+ return map.count(m_token) == 1;
+ }
+
+ bool operator()(const std::shared_ptr<object>& object) const {
+ return object->has(m_token);
+ }
+
+ private:
+ const std::string& m_token;
+};
+
+}