C++ Templates as Partial Evaluation

TL;DR

This paper reinterprets C++ templates as a form of partial evaluation, proposing a unified mechanism that simplifies syntax and integrates generic programming, compile-time computation, and code generation.

Contribution

It introduces a new perspective viewing C++ templates through partial evaluation, and presents the language Catat to demonstrate this unified approach.

Findings

Templates support compile-time computations and code generation.

Recasting templates as partial evaluation simplifies syntax.

Proposes a unified mechanism for generic programming and code generation.

Abstract

This paper explores the relationship between C++ templates and partial evaluation. Templates were designed to support generic programming, but unintentionally provided the ability to perform compile-time computations and code generation. These features are completely accidental, and as a result their syntax is awkward. By recasting these features in terms of partial evaluation, a much simpler syntax can be achieved. C++ may be regarded as a two-level language in which types are first-class values. Template instantiation resembles an offline partial evaluator. This paper describes preliminary work toward a single mechanism based on Partial Evaluation which unifies generic programming, compile-time computation and code generation. The language Catat is introduced to illustrate these ideas.