As of this writing, two of the components of BetterR are compiled using ImportC, the GSL random number generators and the matrix library from Gretl. This is a big win, because we can use well-tested libraries that have been used for years, allowing us to trust that most bugs will have been found and various edge cases have been solved.
Since C files don’t have access to D’s module system, we’re left with two options: we can dump the C source and header files in the project directory, or we can provide the compiler with the information it needs to find those files. Note that this is true even if you have a D wrapper written over the top of the C functionality. The D wrapper needs the location of the C source and header files.
This is what I add to the compilation command for the GSL RNG library:
-P-Igsl/rng gsl/rng/*.cThe -P passes info to the gcc preprocessor. -Igsl/rng tells it to look in gsl/rng (relative directory in this case) for header files. gsl/rng/*.c says to look in that directory for C source files. In the case that I wanted to exclude some of the C files, I’d have to specify them manually. If you’re doing that, in my opinion, you should probably find a better way to organize your files.
I prefer to make it so that the user of the library only imports D modules. The downside of doing that is that the user may not understand why they have to provide the location of C files to the compiler.