Policy-based Design

Policy-based design, also known as policy-based class design or policy-based programming, is a computer programming paradigm based on an idiom for C++ known as policies. It has been described as a compile-time variant of the strategy pattern, and has connections with C++ template metaprogramming. It was first popularized by Andrei Alexandrescu with his 2001 book Modern C++ Design and his column Generic in the C/C++ Users Journal.

Although the technique could theoretically be applied to other languages, it is currently closely associated with C++, and depends on the particular feature set of that language. Furthermore, even in C++ it requires a compiler with highly robust support for templates, which wasn't common before about 2003.