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copied!<p>Realize that smart pointers are compared by comparing the underlying container. So you can just use a <code>std::set</code> of whatever smartpointer you prefer. Personally I use <code>std::unique_ptr</code> over <code>shared_ptr</code>, whenever I can get away with it, since it makes the ownership much clearer (whoever holds the <code>unique_ptr</code>is the owner) and has much lower overhead too. I have found that this is enough for almost all my code. The code would look something like the following:</p> <pre><code>std::set<std::unique_ptr<T> > _list; void SomeClass::add(T* ptr) { std::unique_ptr<T> p(ptr); auto iter = _list.find(p); if(iter == _list.end()) _list.insert(std::move(p)); else p.release(); } </code></pre> <p>I'm not sure right now if that is overkill (have to check if <code>insert</code> is guaranteed not to do anything, if the insertion fails), but it should work. Doing this with <code>shared_ptr<T></code> would look similar, although be a bit more complex, due to the lack of a <code>relase</code> member. In that case I would probably first construct a <code>shared_ptr<T></code> with a do nothing <code>deleter</code> too pass to the call to find and then another <code>shared_ptr<T></code> which is actually inserted.</p> <p>Of course personally I would avoid doing this and always pass around smart pointers when the ownership of a pointer changes hands. Therefore I would rewrite <code>SomeClass::add</code> as <code>void SomeClass::add(std::unique_ptr<T> ptr)</code> or <code>void SomeClass::add(std::shared_ptr<T> ptr)</code> which would pretty much solve the problem of having multiple instances anyways (as long as the pointer is always wrapped).</p>

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