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    <p>You've missed a significant optimization in your copy assignment operator. And subsequently the situation has gotten confused.</p> <pre><code> AnObject&amp; operator = ( const AnObject&amp; rh ) { if (this != &amp;rh) { if (n != rh.n) { delete [] a; n = 0; a = new int [ rh.n ]; n = rh.n; } std::copy(rh.a, rh.a+n, a); } return *this; } </code></pre> <p>Unless you really <em>never</em> think you'll be assigning <code>AnObject</code>s of the same size, this is much better. Never throw away resources if you can recycle them.</p> <p>Some might complain that the <code>AnObject</code>'s copy assignment operator now has only basic exception safety instead of strong exception safety. However consider this:</p> <blockquote> <p>Your clients can always take a fast assignment operator and give it strong exception safety. But they can't take a slow assignment operator and make it faster.</p> <pre><code>template &lt;class T&gt; T&amp; strong_assign(T&amp; x, T y) { swap(x, y); return x; } </code></pre> </blockquote> <p>Your move constructor is fine, but your move assignment operator has a memory leak. It should be:</p> <pre><code> AnObject&amp; operator = ( AnObject&amp;&amp; rh ) { delete [] a; n = rh.n; a = rh.a; rh.n = 0; rh.a = nullptr; return *this; } </code></pre> <p>...</p> <blockquote> <pre><code>Data a = MakeData(); Data c = 5 * a + ( 1 + MakeMoreData() ) / 3; </code></pre> <p><strong>q2:</strong> Using a combination of copy elision / RVO / move semantics the compiler should be able to this this with a minimum of copying, no?</p> </blockquote> <p>You may need to overload your operators to take advantage of resources in rvalues:</p> <pre><code>Data operator+(Data&amp;&amp; x, const Data&amp; y) { // recycle resources in x! x += y; return std::move(x); } </code></pre> <p>Ultimately resources ought to be created exactly once for each <code>Data</code> you care about. There should be no needless <code>new/delete</code> just for the purpose of moving things around.</p>
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    1. POHow to actually implement the rule of five?
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    1. COthanks, you made some good points. I guess the only way to know if this implementation is more performant than Anthony's is to measure it. Also for the operator overloads, I already figured there would be a lot of them since they should be defined both for Data objects and scalars. Possible solution here: http://stackoverflow.com/questions/2696156/how-to-reduce-redundant-code-when-adding-new-c0x-rvalue-reference-operator-over
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    2. COI'm going to downvote this, because it would be trivial to make the copy assignment operator strongly exception safe and I definitely think that you should.
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    3. CO@DeadMG: Thanks for identifying your downvote. I so strongly disagree with your position that I will gladly accept a million downvotes without changing my position. The copy/swap idiom is little more than a poor man's move assignment operator for C++03. Once you have a real move assignment operator in your toolbox, it is not logical to blindly continue along that path. Everyone interested should count allocations and measure performance. Test both lvalue and rvalue rhs's. Test your common use cases. Otoh, if you do not care about performance then move members are a waste of time.
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