C∀ Type System Implementation

Abstract

The C programming language has been an important software development tool for decades. C∀ is a new programming language designed with strong backwards-compatibility to take advantage of widely distributed C programming expertise and the large deployed base of C code, paired with modern language features to improve developer productivity.

This thesis presents a number of improvements to C∀. The author has developed one major new language feature, generic types, in a way that integrates naturally with both the existing polymorphism features of C∀ and the translation-unit-based encapsulation model of C. This thesis also presents a number of smaller refinements to the C∀ overload resolution rules, each of which improves the expressivity or intuitive nature of the language.

This thesis also includes a number of practical improvements to C∀ compilation performance, focused on the expression resolution pass, which is the main bottleneck. These include better algorithms for argument-parameter matching and type assertion satisfaction, as well as a new type-environment data-structure based on a novel variant of union-find. The compilation performance improvements have all been experimentally validated with a new prototype system that encapsulates the key aspects of the C∀ language; this prototype is a promising basis for future research and a technical contribution of this work.

C∀, extended and refined in this thesis, presents both an independently interesting combination of language features and a comprehensive approach to the modernization of C. This work demonstrates the hitherto unproven compiler-implementation viability of the C∀ language design, and provides a number of useful tools to implementors of other languages.