Which other languages use the C/C++ preprocessor? I've seen it used for generating data or other source code when a preprocessor comes in handy, but never as a full-fledged component of another language.
I also think that a modern language that uses includes instead of modules is just outright insane.
Objective-c introduced `#import`, which guards from double including by default. I would suspect and performance gains are tempered with a "pure" objc project.
The Glasgow Haskell Compiler has a language pragma for running CPP before compilation. I've seen it used a few times, for #ifdef compatibility between Windows and Linux for low-level stuff. I don't think anyone would ever want to use #include or macros, so the issue of speed is not very interesting in that context.
Could you substantiate this claim? I don't necessarily not believe you, but it's an easy claim to make without any quantifiable argument. It's also hard to test against eg clang, where preprocessing is performed in the same process as the compiler and assembler, and the performance of a preprocessor is really less interesting than total compile time.
Let me clarify—could you substantiate the performance claims? I have no doubt it's a correct preprocessor, but I do have doubts about performance claims in the context of the compilation of a project. cpp (and the rest of the gnu compiler toolchain) itself is a pretty terrible example of a well-written program, but clang is a well-written, holistic, performance-centered program, and it would strike me as difficult for an isolated preprocessor to improve significantly on it compared to the built in one.
Or another way of putting this is—you speak compellingly about both the algorithm side and the constant side (no tokenizing), but you don't speak about "real world" performance when interacting with many levels of caches, processes, and filesystems. Could you speak to this at all?