I had a quick brain BSOD reading the code because lot's of things have yy_ prefixes but the code is actually written by hand, not generated by Yacc/Bison.
Yes, I used the 'yy_' prefix to indicate that they are parsing-related functions, and also as a tribute to Yacc/Bison. You're not the first person who finds this creepy. Maybe I should change the prefix...