Program generation is indispensable. We propose a novel unification of two existing metaprogramming techniques: multi-stage programming and hygienic macros. The former supports runtime code generation and execution in a type-safe manner while the latter offers compile-time code generation.

In this work we draw upon a long line of research on metaprogramming, starting with Lisp, MetaML and MetaOCaml. We provide direct support for quotes and splices, regulated by a Phase Consistency Principle. The latter simplifies the treatment of open code without sacrificing expressiveness. Our design enables the construction and combination of code values for both expressions and types. Moreover, code generation can happen either at runtime à la MetaOCaml or at compile time in a macro fashion.

We provide an implementation of our design in Scala and we present two case studies. The first implements the Hidden Markov Model, Shonan Challenge for HPC. The second implements the staged streaming library Strymonas.