Use templates to express algorithms that apply to many argument types

Reason

Generality. Minimizing the amount of source code. Interoperability. Reuse.

Example

That's the foundation of the STL. A single find algorithm easily works with any kind of input range:

template<typename Iter, typename Val>
    // requires Input_iterator<Iter>
    //       && Equality_comparable<Value_type<Iter>, Val>
Iter find(Iter b, Iter e, Val v)
{
    // ...
}

Note

Don't use a template unless you have a realistic need for more than one template argument type. Don't overabstract.

Enforcement

??? tough, probably needs a human