Implementing Signatures for C++

In this paper we overview the design and implementation of a language extension to C++ for abstracting types and for decoupling subtyping and inheritance. This extension gives the user more of the flexibility of dynamic typing while retaining the efficiency and security of static typing. We discuss the syntax and semantics of this language extension, show examples of its use, and present and analyze the cost of three different implementation techniques: a preprocessor to a C++ compiler, an implementation in the front end of a C++ compiler, and a low-level back-end based implementation.