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    copied!<p>As far your problem is described you have a collection of dynamically allocated polymorphic objects.</p> <p>The solution can change depending on how these object adhere to certain design disciplines:</p> <ol> <li>are you object "leaf only objects"? (not referring to other object themselves)?</li> <li>are there just single acyclic references (do your object form only trees of subobjects)?</li> <li>are there multiple path between references (a same object referred by two or more)</li> <li>are there cyclic references?</li> <li>are there references to other object <em>members</em>?</li> </ol> <p>The situation can become very complex depending on the situation and depending if you can tolerate or not multiple output of a same object and how can you break eventual loops.</p> <p>A first thing you cannot do is use <code>Base</code> as a value parameter (like in your , since that creates a copy (admitting your objects are copyable: if they refer to other object what does a copy do? multiplies the paths? Clones the referred object as well?)</p> <p>If you are in situation (1.), you just need a virtual function taking <code>std::ostream&amp;</code>, to be overridden in all the leaf objects. Then you need an overload for <code>operator&lt;&lt;(std::ostream&amp;, Base*)</code> and another for <code>(std::ostream&amp;, const std::vector&lt;Base*&gt;&amp;)</code></p> <p>like this:</p> <pre><code>class Base { ... public: virtual ~Base() {} //must be polymorphic protected: virtual void out(std::ostream&amp; s) =0; friend std::ostream&amp; operator&lt;&lt;(std::ostream&amp; st, Base* pb) { pb-&gt;out(st); return st; } }; class Derived1: public Base { ... protected: virtual void out(std::ostream&amp; s) { s &lt;&lt; "Derived1 at " &lt;&lt; this &lt;&lt; " address " &lt;&lt; std::endl; } }; class Derived2: public Base { ... protected: virtual void out(std::ostream&amp; s) { s &lt;&lt; "Derived2 at " &lt;&lt; this &lt;&lt; " address " &lt;&lt; std::endl; } }; std::ostream&amp; operator&lt;&lt;(std::ostream&amp; s, const std::vector&lt;Base*&gt;&amp; v) { s &lt;&lt; "there are " &lt;&lt; v.size() &lt;&lt; " objects:" &lt;&lt; std::endl; for(auto&amp; i:v) s &lt;&lt; i; return s; } </code></pre> <p>If you are in sutuation (2.) yopu may ave a </p> <pre><code>class Derived3: public Base { ... Base* ptrOwnedobject; }; </code></pre> <p>You can simply implement the <code>Derived3::out</code> function to recourse into the owned child.</p> <p>If you are in situation (3.), and you cannot tolerate a same object to be printed more time you ave different parents sharing a same child. You should somehow mark the child so that you don't save it twice or more, and un-mark all of the children after finishing the printing (you will most likely set up that mechanism into the Base class).</p> <p>If you are in situation (4.) then what said about (3.) becomes mandatory to avoid infinite recursion.</p> <p>If you are in situation (5.) you must also discover which object a member belongs (not trivial). If you also have multiple inheritance and virtual bases... things are even more complex.</p>
 

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