The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
// full specialization for BoolString::getValue<>() for bool
template<>
inline bool BoolString::get<bool>() const {
return value == "true" || value == "1" || value == "on";
}