C++ for Scientists - Technische Universität Dresden

6.5. BARTON-NACKMAN TRICK 197
};
bracket proxy operator[](int r) const
{
return bracket proxy(static cast(∗this), r);
}
class matrix : public crtp matrix
{
// ...
};
Once we have such a CRTP class we can provide a bracket operator for every matrix class with a
binary application operator. In a full-fledged linear algebra package one needs to pay attention
which matrices return references and which are mutable but the approach is as described above.
Several timings have shown that the indirection with the proxy did not create run-time overhead
compared to the direct usage of the binary access operator. Apparently, the compilers optimized
the creation of proxies away in the executables.