6. More template internals

• A template makes demands on the types that user wants to use in place of template paremeters such as ValueT.

• If demands aren't satisfied, it's an error.

• So in a way, a template is a client of the typename ValueT, without knowing what ValueT is yet.

• Native C++ types allow lots of operations, so they should almost always be considered first.

• Templates are another reason to have overloaded operators,

  • and to have them behave like the native types do.