Programs are generally constructed using designs that map relatively well on the mechanisms offered by a chosen programming language. Because templates are a whole new language mechanism, it is not surprising to find that they call for new design elements. We explore these elements in this part of the book.
Templates are different from more traditional language constructs in that they allow us to parameterize the types and constants of our code. When combined with (1) partial specialization and (2) recursive instantiation, this leads to a surprising amount of expressive power. In the following chapters, this is illustrated by a large number of design techniques:
Generic programming
Traits
Policy classes
Metaprogramming
Expression templates
Our presentation aims not only at listing the various known design elements, but also at conveying the principles that inspire such designs so that new techniques may be created.
