My Favorite C++ Pattern: X Macros (2023)

When I first joined the Chapel team, one pattern used in its C++-based compiler made a strong impression on me. Since then, I’ve used the pattern many more times, and have been very satisfied with how it turned out. However, it feels like the pattern is relatively unknown, so I thought I’d show it off, and some of its applications in the Chapel compiler . I’ve slightly tweaked a lot of the snippets I directly show in this article for the sake of simpler presentation; I’ve included links to the original code (available on GitHub) if you want to see the unabridged version. Broadly speaking, the “X Macros” pattern is about generating code. If you have a lot of repetitive code to write (declaring many variables or classes, performing many very similar actions, etc.), this pattern can save a lot of time, lead to much more maintainable code, and reduce the effort required to add more code. I will introduce the pattern in its simplest form with my first example: interning strings . Applica ... Read full article.