C is also a functional programming language

Why not? I can just avoid side-effects. I can also treat functions as first-order data using Function pointers.

>>1
I use the approach of macro-based symbolic composition in void.h,
a symbol can be a macro,string of code, a tuple or anything that can be parsed by C preprocessor as argument.
It looks a bit ugly with all repetition-emulating-recursion but its fairly fast and the code is much faster than any lithp