Re: [Boost-users] [review][assign] Formal review of Assign v2 ongoing

23 Jun 2011


      On 21/06/11 23:05, Simonson, Lucanus J wrote:
...
er wrote:
...
You say "I ordinarily only initialize containers to literals when
writing unit tests.". In this case, I think you are right that you
can't beat C++0x initializer lists. But, you still may need to fill a
container, as above. And also, consider the cases below:
#include <vector>
#include <queue>
#include <string>
#include <tuple>
#include 
int main()
{
     typedef std::string s_;
     {
         typedef std::tuple t_;
         typedef std::vector v_;
         v_ v1 = {
             t_( "a", 1 ),
             t_( "b", 2 ),
             t_( "c", 3 ),
             t_( "d", 4 ),
             t_( "e", 5 )
         };
         using namespace boost::assign::v2;
         v_ v2 = converter(
             csv_deque( "a", 1, "b", 2, "c", 3, "d", 4, "e", 5)
         );
     }
No, initializer lists can apply to the elements and be nested.
v_ v1 = {
              { "a", 1 },
              { "b", 2 },
              { "c", 3 },
              { "d", 4 },
              { "e", 5 }
          };
Arguably the extra {} around each vector element in the new
initializer syntax is more readable than the proposed assign
v2 syntax.  Tuple and deque support initializer list as do
all classes with constructors and structs.
For what it's worth, your particular example doesn't work in gcc 4.5
because the relevant constructor of std::tuple's is explicit (I wasn't
aware of this effect of marking a constructor explicit, and I'm quite
surprised...).  The analogous example with std::pair works fine.

John Bytheway