Re: (Spirit) Semantic Actions with member functions?

From: Slava Akhmechet (yg-boost-users_at_[hidden])
Date: 2003-05-09 15:54:26

I was able to get boost::bind working to bind the semantic action to the member function of MyGrammar. This seems like a superior solution. In any case, I am not sure how to pass custom data to a functor. When specifing a semantic action I have to pass the type of the functor, which implies that spirit creates a temporary object. Am I missing something?

> Its time to switch your global function "myaction" into a functor.
> Functors are classes that have a function call operator with the same
> synopsis as your function.
> The advantage is that one can pass custom data to it via a non-default
> constructor.
> 
> Functors should be and sometimes must be stateless, so care must be
> employeed to use references in member data.
> 
> Slava Akhmechet wrote:
> 
> > I am playing around with Spirit and I seem to run into an architecture
> > problem with semantic actions. Here's a small example.
> >
> > class MyGrammar : public grammar<MyGrammar>
> > {
> > public:
> > template <typename ScannerT>
> > struct definition
> > {
> > definition(MyGrammar const& self)
> > {
> > TestRule = str_p("test")[&my_action];
> > }
> >
> > rule<ScannerT> const&
> > start() const { return TestRulet; };
> >
> > private:
> > rule<ScannerT> TestRule;
> > };
> > };
> >
> > My major problem is related to the fact that I cannot pass any custom
> > data to my_action function. Since my_action is a global function, it
> > has no knowledge of MyGrammar and must rely on global variables.
> > Ideally, I would pass self to my_action to be able to hold state. What
> > is a general way to get around this problem? The documention mentions
> > a way to specify member functions as semantic action actors using
> > boost's bind facilities but I was unable to get it to work.
> > Thanks in advance.
> >
> > P.S. Sorry for a fairly newbie question, I was unable to find the
> > answer online or in the docs.
> > P.P.S. I might have accidently double posted this. Sorry about that.
> >
> >
> >
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