@clacke @craigmaloney @arunisaac I asked in #guile, janneke says:

- nyacc is used by mes, but is now unbundled from it.
- nyacc is a C99 parser, ie C99 -> AST
- mescc is a C99 compiler, ie AST -> M
- mes is a scheme interpreter that can run mescc
- nyacc in an amazing parser generator framework that comes with an almost complete c99 parser and preprocessor

(Thanks janneke!)