On Sun, 18 Jul 2010, Panayiotis Karabassis wrote:
> The problem is that I would like to select different start symbols at
> run-time.
Where start is your original start symbol, extend your grammar like this:
start_extended:
start
| TK_EXPRESSION expression
| TK_FOO foo
;
At run-time, if you want to test expression, set a flag that causes your
scanner to return TK_EXPRESSION before scanning the input. Likewise for
foo and TK_FOO.
A push parser makes this even easier because you can push TK_EXPRESSION or
TK_FOO to the parser before pull-parsing the rest of the input stream, so
you don't have to implement flags to direct the scanner. However, we
haven't implemented push parsing for C++ yet.
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