A long time ago, I had to write SQL parsers (for 3 of the most popular DBs at the time). It is a surprisingly difficult language to parse and disambiguate - particularly when having to deal with the warts of its variants. Sure it's not quite C++ but it's was easily the most annoying parser work I ever had to do. And in my experience, the trickier it is to parse a particular language, the more difficult it is to provide feedback to users in the form of helpful parse errors.