Re: [Boost-users] Is there such stuff in boost?

6 May 2008

      ...
#include 
#include 
#include <cassert>
int main()
{
 typedef boost::reference_wrapper<double> double_ref_t;
 boost::array array;
double_ref_t d0( array[0] );
 double_ref_t d1( array[1] );
array[0] = 1.0;
 array[1] = 2.0;
 assert( d1 == 2.0 );
d0 += d1;
 assert( d0 == 3.0 );
}
Thank you for your reply, I've also walked through the brief documentation
of Ref (There's even not a simple example showing its usage and power!)

The solution you provided is nearly what I need. My main intention is to get
the ability to group/organize scattered/individual variables of a same type
into a standard container (vector or so) to enable fast/elegant traversal in 
one run with one or two lines of code (with a call to for_each() or similar),
without doing the same operation one by one with these individual variables.

With your solution, I should declare my varaibles of type T, on which I will 
do some operation in the future, as boost::reference_wrapper<T>. Obviously 
to me for any arbitrary type, class reference_wrapper<T> will not automatically
delegate all the functionality of T. That's why I'm not saying this is EXACTLY
what I need. And remember to delcare T as reference_wrapper<T> for a variable
is an extra burden to me. :-)

In the meantile, your code is no different to the following much simpler form:

	boost::array array;

	double & d0 = array[0];
	double & d1 = array[1];

	array[0] = 1.0;
	array[1] = 2.0;
	assert( d1 == 2.0 );

I also tried the following code snnippet:

	typedef boost::reference_wrapper<double> double_ref_t;

	double d0, d1, d2, d3;
	boost::array array = {{boost::ref(d0), boost::ref(d1), boost::ref(d2), boost::ref(d3)}};
 	for(int i=0; i<4; i++) array[i] = 2.0;
 	assert(d2 == 2.0);
	return 0;

It seems closer to what I need but, in fact, it has the same restriction. And, even worse, it didn't get compiled.

Thank you anyway for your help!
Still expecting more exiciting solutions!

B/Rgds
Max