I'm totally aware of Rustler :) but it's a nice tool to share! I was mostly trying to speak to the real world environment where you have a simple routine or interface already prepackaged and you want access to it... Not that you can't use Rustler, but just being able to access the C interface directly is comforting (and sometimes easier than adding another compilation step between them even if it is _safer_ (e.g. prototyping)).