Do you know about variable templates?
by Yu Xuan Zhang
From the article:
The variable template, which comes from N3651, is one of the major proposals in Standard C++14. The main purpose of the variable template is to simplify definitions and uses of parameterized constants.
Rules before C++14 do not allow declaring a variable using a template declaration. There are workarounds for this problem before C++14, but they are either redundant or complicated...