On Sun, 9 Oct 2011, Christoph wrote:
Hi
recently i started programming with the boost graph library. You can use nice syntax for iterating over a set of vertices or edges by writing for example:
//begin program #include <iostream> #include
typedef boost::adjacency_list < boost::listS, boost::vecS, boost::bidirectionalS> my_graph;
typedef boost::graph_traits
my_graph_traits; int main() { my_graph g(5); my_graph_traits::vertex_iterator vi, vi_end;
for (boost::tie (vi, vi_end) = vertices (g); vi != vi_end; ++vi) { std::cout << "vertex: " << *vi << std::endl; } } //End program
Outputs: vertex: 0 vertex: 1 vertex: 2 vertex: 3 vertex: 4
My question is now how to define functions 'tie(...)' and 'elements(...)' for using them with standard containers.
Suppose you have a container like the list:
std::list <unsigned int> list(4);
Now to iterate over all elements i would like to write something like
//begin snippet std::list <unsigned int>::iterator begin, end; for (tie (begin, end) = elements (list); begin != end; ++begin) ;// do some thing //end snippet
In stead of writing:
//begin snippet begin = list.begin(); end = list.end();
for (; begin != end; ++begin) ;// do some thing //end snippet
I started defining the function elements(...) like this:
template <typename T> std::pair < typename T::iterator, typename T::iterator> elements (T container) { return std::make_pair(container.begin(), container.end()); }
The compiler tells me, that 'tie' was not declared in this scope. So i assume that i also have to define the 'tie' function in some way. Maybe there is already some functionality to access the standard containers the way you can do it with 'tie' or maybe you could give me some hint to solve the problem.
You need to use boost::tie if your iterator types are not already in the boost namespace. The definition of tie is in Boost.Tuple, I think. -- Jeremiah Willcock