Function Template Declaration

You must declare a template before you can use it. A declaration, as in the following example, provides enough information to use the template, but not enough information to implement the template.

template <class Number> Number twice( Number original );

In this example, Number is a template parameter; it specifies the range of functions that the template describes. More specifically, Number is a template type parameter, and its use within template declarations and definitions stands for some to-be-determined type.