void lexer_roll_back(struct lexer_book *bk, int offset)
{
while(offset > 0) {
offset--;
lexer_roll_back_one(bk);
}
}
void lexer_roll_back(struct lexer *lx, int offset)
{
while(offset > 0) {
offset--;
lexer_roll_back_one(lx);
}
}