Re: [boost] [spirit] semantic action for mismatches?

Subject: Re: [boost] [spirit] semantic action for mismatches?
From: caustik (caustik_at_[hidden])
Date: 2011-01-08 12:39:38

On Sat, Jan 8, 2011 at 9:19 AM, Hartmut Kaiser <hartmut.kaiser_at_[hidden]>wrote:

> > I might give that a shot as I can't seem to get local variables to solve
> > my problem. I would expect these two commands to have the same result
> > (albeit unnecessarily assigning the _a variable, which just gets tossed
> > away anyway), but apparently they are not?
> >
> > r = p[_a = _1]
> > r = p
>
> Automatic attribute propagation from the rhs expression to the lhs rule is
> disabled as soon as semantic actions are involved. If you want to enforce
> attribute propagation anyways, write:
>
>    rule<...> r;
>    r %= p[...];
>
> If the rhs has no semantic actions attached, operator=() behaves exactly
> like operator%=().
>

That does the trick. Apologies for the previous top-post. I've been out of
the mailing list game for a while now =)

This style ended up working and I can finally move on to other things:

r %= p1[_a = _1] >> ('*' | (eps[bind(&class::undo, &instance, _a)] >> !eps))
>> p2