Re: [Boost-users] Spirit: Assigning elements of a closure member.

6 Apr 2006

      Having failed to find this elsewhere in boost, or in spirit, I rolled my 
own - and it turned out to be a lot simpler than I expected:-

   struct assign_member_impl
   {
      template 
      struct result
      {
         typedef void type;
      };
      template 
      void operator()(Container& c, Member &m, Item const& item) const
      {
         c.*m = item;
      }
   };
   function const assign_member_a = 
assign_member_impl();

In a semantic action, we can then do something like this:-
  myrule = int_p[assign_member_a(myrule.m1, &foo::a, arg1)];

Mark

"Mark Williams"  wrote in message 
news:e10t9b$86l$1@sea.gmane.org...
...
Is there any standard way, in a semantic action, to assign individual 
elements of a struct that is set as a member of a closure? For example 
suppose I have:-
struct foo {
 int a, b, c;
 std::string d;
 float e;
};
And I have this as member1 in my closure, which is then attached to a rule 
that parses each of those struct member elements seperately, is there then 
a standard way within the semantic actions in my rule to assign to foo.d, 
say, without modifying the other values? It seems that my only option is 
to either write my own functors to set each member seperately, or have the 
individual elements as seperate members of my closure.
I kind of want to do something like this:
myrule = int_p[assign_a(myrule.m1.a)] >> int_p[assign_a(myrule.m1.b)];
But myrule.m1 is an actor, not an instance of foo.
Is there a way to do this with boost::bind perhaps?
I want to use closures since my rules need to be reentrant.
Mark