C++14 Variable Templates: what is their purpose? Any usage example?

Question

C++14 will allow the creation of variables that are templated. The usual example is a variable \'pi\' that can be read to get the value of the mathematical constant π for va

Answer 1

Another practical example for C++14's variable templates is when you need a function for passing something into std::accumulate:

template
T const & (*maxer) (T const &, T const &) = std::max;

std::accumulate(some.begin(), some.end(), initial, maxer);

Note that using std::max is insufficient because it can't deduce the exact signature. In this particular example you can use max_element instead, but the point is that there is a whole class of functions that share this behavior.