The Ekeko/X Program Transformation Tool

Developers often need to perform repetitive changes to source code. For instance, to repair several instances of a bug or to update all clients of a library to a newer version. Manually performing such changes is laborious and error-prone. Program transformation tools enable automating changes, but specifying changes as a program transformation requires significant expertise. Code templates are often touted as a remedy, yet have never been endorsed wholeheartedly. Their use is mostly limited to expressing the syntactic characteristics of the intended change subjects. Less familiar means have to be resorted to for expressing their structural, control flow, and data flow characteristics. In this tool paper, we introduce a decidedly template-driven program transformation tool called Ekeko/X. Its specifications feature templates for specifying all of the aforementioned characteristics of its subjects. To this end, developers can associate different directives with individual components of a template. Each matching directive imposes particular constraints on the matches for the component it is associated with. Rewriting directives, on the other hand, determine how each match should be changed. We develop Ekeko/X from the ground up, starting from its applicative logic meta-programming foundation. We highlight the key choices in this implementation and demonstrate its use through two example program transformations.