On 1/8/2011 9:57 AM, caustik wrote:
On Fri, Jan 7, 2011 at 5:30 PM, Joel de Guzman<joel@boost-consulting.com>wrote:
On 1/8/2011 7:54 AM, caustik wrote:
I've come to notice that there seems to be a missing bit of symmetry in spirit with regards to semantic actions.
If a rule matches, and thus executes it's semantic action(s), but a rule which includes that rule mismatches, there seems to be no way to "unwind" the code executed down the chain. For example, if one of your semantic actions allocates memory or increments a reference count, how do you free / release that reference in the mismatch scenario? I've thought about using something like a shared_ptr, but it seems like that gets pretty sloppy and unnatural. Is there something you can think of that would work?
Sure:
r = p | eps[cleanup];
If p fails with side-effects from its direct or indirect semantic actions, the cleanup semantic action can roll them back. <http://spirit.sf.net>
hmmm...
Brilliant. You sir, are a gentleman and a scholar.
<blush> That was an easy way to earn that comment :-)
I wonder if this is FAQ material. It's elegant yet a bit non-intuitive.
There is now: http://boost-spirit.com/home/articles/doc-addendum/faq/ Thanks! Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net