Re: How to implement optional semicolon rules

[Matthias Simon]

Hi again,

I want to share my solution with you and the future generations 
stumbling across similar problems ;) I decided implementing the exact 
semicolon rules was not worth the trouble:

- The grammar is already quite complex and difficult to understand, 
changing these to respect semicolon rules is a waste of effort
- Let bison instruct the lexer when to inject a semicolon, like 
<<OptSemicolon: { driver->inject_semicolon = 1; } ';'>>, did not work 
out, because when the mid-action is executed, bison already has read the 
next token, so it is to late to inject. But moving this action one token 
earlier would cause the lexer to inject semicolon in the wrong places.

So, I just made all semicolons optional and tried to cope with the 
conflicts. I just had two kinds of conflicts ( \o/ ), actually. One 
--probably a quite common-- was:

Stmt:
    ...
    | "return"
    | "return" Expression
    | Assignment
    ....

Expression and Assignment both may begin with an identifier. So bison 
does not know whether to shift for the second option or to reduce the 
first and start with the Assignment. The default --shifting the 
Expression-- totally works for me. First because, having an Assignment 
right after a `return' does virtually never appear, secondly the 
type-checker is able dectect a `mis-shifted' return and could suggest an 
explicit semicolon.

Problem solved. Thank you a lot for your support :)

Cheers,

Matthias