Question

I ran into some trouble while using a list of arrays.
So to clear things up I do know that I can’t have a std::list containing arrays.
I am using boost::array to be able to do that.

Currently I prototype all datatypes needed for my pathfinding algorithm and test them for speed and cache coherence.

typedef boost::array<int,2> VertexB2i;
typedef std::list<VertexB2i> VertexList;

These types are not used for pathfinding, they are simply easier to use then all the real c++ arrays and flags for the pathfinder, so they are just used to generate a navigation mesh.
(I also know I could use a stl::pair instead boost::array in this case, but I want to keep the generated data as similar to the pathfinders data as possible, so I don’t have to deal with two totally different interfaces the whole time)

VertexList* vl = new VertexList();
vl->push_back({{8,28}}); // this does not work, why?

So while setting up some testing data for these two data-types, I noticed that the commented line does not work, although this does work:

VertexList* vl = new VertexList();
VertexB2i ver1 = {{8,28}};
vl->push_back({ver1}); // works

So to sum it up:
Is there anyway to pushback a “VertexB2i” without declaring it separte first?
General advices?

Answer 1

std::array (or boost::array) is an aggregate type. In C++98/03 it can only be initialized in the declarator:

std::array<int, 2> arr = { 1, 2 };
thelist.push_back(arr); // makes a copy

In C++11, you can use uniform initialization to create temporaries as well:

std::list<std::array<int,2>> l;

l.push_back(std::array<int,2>{{2,3}});     // maybe copy
l.emplace_back(std::array<int,2>{{2,3}});  // maybe copy, probably optimized out