Re: [Boost-users] [phoenix] function with reference implementation

11 Sep 2010


      On Sep 10, 4:36 pm, Joel de Guzman  wrote:
...
On 9/11/10 4:37 AM, alfC wrote:
...
I noticed that in some contexts I have both the object class and the
corresponding phoenix function
...
   class impl;
   ...
...
   impl f_impl;
   boost::phoenix::function<impl>  f(f_impl);
...
now to avoid the copying I could use:
...
   boost::phoenix::function  f(f_impl);
...
which works. Although
   boost::phoenix::function  f(f_impl); //doesn't work.
(error below)
...
Is there any problem with using references at all, in the first place?
I'm not sure. Could you provide a minimal cpp file I can try?
Yes, see below. Althougth now that I made this example I realize that
the underlying object implementation is copied many times anyway (at
least 4 times in the example), I guess during the building up of the
expression template. [The final objective was to make an object
function that not only evaluates but also is able to take expression
and build expression templates].

#include
#include<iostream>
struct F{
	double a_;
	F(double a) : a_(a){std::cout << "F constructed" < pf(f);
		std::cout << pf(arg1+1.)((double const&)5.) << std::endl;
	}
	/* block doesn't work
	{
		F f(4.);
		boost::phoenix::function pf(f); //does not compile
		std::cout << pf(arg1+1.)((double const&)5.) << std::endl;
	}
	*/
}

prints:
F constructed
F copied
F copied
F copied
F copied
F copied
144
F constructed
F copied
F copied
F copied
F copied
144