DSL in C++ template metaprogram

Abstract

Domain specific language integration has to provide the right balance between the expressive power of the DSL and the implementation and maintenance cost of the applied integration techniques. In this paper we discuss a DSL integration technique for the C++ programming language. The solution is based on compile-time parsing of the DSL code using the C++ template metaprogramming library called Metaparse. The parser generator is the C++ template metaprogram reimplementation of a runtime Haskell parser generator library. The full parsing phase is executed when the host program is compiled. The library uses only standard C++ language features, thus our solution is highly portable. As a demonstration of the power of this approach, we present a highly efficient and type-safe version of printf and the way it can be constructed using our library. Despite the well known syntactical difficulties of C++ template metaprograms, building embedded languages using Metaparse leads to self-documenting maintenable C++ source code.