linqit VS fypp

most of it's just general programming niceness. If you have to spend a few hours to wrestle with make/bazel/etc every time you need to reach for a dependency, you don't depend on things and have to rewrite them yourself. If your programming language doesn't have good ways of writing generic code, you either have to write the code once per precision (and do all your bugfixes/perf improvements in triplicate) or do very hacky metaprogramming where you use Python to generate your low level code (yes the Fortran people actually do this https://github.com/aradi/fypp), or use the C preprocesser which is even worse.

Please don't use #define in Fortran. It is not standard compliant. There is no guarantee that anything will ever be done about a # symbol in your code. There is no Fortran preprocessor (though there are a few open projects example). Also, if you're working with Fortran developers they'd expect to see integer. Also, we don't have the same guarantees of variable sizes like in C soF64andI32may be misleading unless you're usingISO_C_BINDING` or similar.

If you really really need to reduce code size for future projects, you might want to use preprocessors like FYPP. It basically insert code snippets at specified points in your code. It's also very helpful for automating the copy-pasting of redundant codes.

If you are fine with using a preprocessor, you could use Fypp for example instead of include files.