Expressing structural properties as language constructs

A program should document its organization and decisions about the programming process. Since the programmer's thinking about programming and program organization continually evolves, languages inevitably prove unable to state these decisions in a precise and adequate fashion. Macro systems could provide a convenient way to extend a language with such statements, if they had more structure than traditional C- and Lisp-style macros provide. With our system, McMicMac, designers can express a variety of specifications as language constructs, including program representations of design patterns, high-level recursive programming operators, and collaboration-based design mechanisms. Unlike traditional macro systems, McMicMac offers a simple yet powerful means for describing specifications, prevents unintentional name clashes, provides feedback in terms of the programmer's source, and has modular mechanisms for managing specifications. We have implemented and used McMicMac to define several groups of extensions.