- bool operator<(const Tag &t) const { return id<t.id; }
- bool operator==(const Tag &t) const { return id==t.id; }
+ std::string str() const;
+
+ bool operator<(Tag t) const { return id<t.id; }
+ bool operator==(Tag t) const { return id==t.id; }
+ bool operator!=(Tag t) const { return id!=t.id; }