Re: Bison & flex on start conditions

[Evan Lavelle]

Henrik Sorensen wrote:

> For the pl1 problem, I cheated a bit with flex, and when certain conditions 
> are met I simply save all the token met, and then change them to what I need 
> before returning the tokens to bison. If you are interested in more feel free 
> to contact me, or better look at the code (pl1gcc.sourceforge.net).

This is great if you can do it, but it means that you're doing the 
parsing in lex ('when certain conditions are met'). If your analysis is 
so complex that you can't do it in lex, then you really need to do it in 
bison, where you run into the potential look-ahead problem. What makes 
the problem even worse is that you're not even guaranteed that there 
*is* a look-ahead token: sometimes there is, sometimes there isn't.

Evan