@NOTimothyLottes Actually on my end, I'd already be happy to see just function pointer constants that could be fully inlined at compile time. This would be quite easy probably, but GLSL doesn't offer even this. Maybe with another layer of ugly macros I could make something work...

See for instance examples here: https://iquilezles.org/articles/sdfrepetition/
Every time there's an "sdf()" call represents a use for a function pointer that could be known at compile time and still make code reusable.