I created one a long time ago for reasons that seem to show up in others. Those included: Lisp-style macros are raw productivity/power; incremental, per-function compilation plus REPL = blazing, iteration speed; if using LCD of features, I can synthesize to more than one language/VM target; I can automate safety checks for C pitfalls without looking at cluttered code; way cleaner way to handle errors with similar benefit.
Sadly, I lost that tool in a triple, HD crash along with most work. Loved it, though. I never even fully learned LISP or C but the subsets let me crank out tons functionality really fast then run it through optimizing C compilers.
It didn't exist at the time. I was gonna maybe turn it into a product, too. That be a great default today, though. Now I also know one can have paid, shared source. I might have opened it with free, perpetual licenses for any contributors.
Sadly, I lost that tool in a triple, HD crash along with most work. Loved it, though. I never even fully learned LISP or C but the subsets let me crank out tons functionality really fast then run it through optimizing C compilers.