>How does that work? It doesn't seem obvious to me? Assume that "-" is the MINUS token. This means that, starting with the first character in "a", we have the

>How does that work? It doesn't seem obvious to me? Assume that "-" is the MINUS token. This means that, starting with the first character in "a", we have the token string "A MINUS B", which we can determine with a 3 token lookahead. Now, if either A or B are reserved keywords, the lexer knows that "A MINUS B" is not correct (unless the grammar happens to allow for a keyword to occur next to a minus sign, which I don't think Java does. If it does, then you just avoid using that keyword when deriving a new one). At this point, the lexer and lex it as "A-B", which is (hopefully) a keyword. I can't think of any examples, but I feel like I have seen languages reserve take a simmiliar approach where they reserve a prefix, which allows them to create as many new reserved words as they like.