boost geometry distance() error in compile

Question

I just write a simply example given by boost (http://www.boost.org/doc/libs/1_52_0/libs/geometry/doc/html/geometry/quickstart.html). There are some errors during compiling. I use eclipse and Mingw to compile it. Could someone tell me what's the problem?

The test code is as follows:

#include <iostream>
using namespace std;

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/algorithms/distance.hpp>

using namespace boost::geometry;

int main() {
cout << "!!!Hello World!!!" << endl; 
model::d2::point_xy<int> p1(1, 1), p2(2, 2);
cout << "Distance p1-p2 is: " << distance(p1, p2) << endl;
return 0;
}

The error is as follows:

c:\program files\mingw64\bin\../lib/gcc/x86_64-w64-  
mingw32/4.7.1/include/c++/bits/stl_iterator_base_funcs.h:114:5:   
required by substitution of 'template<class _InputIterator> 
typename std::iterator_traits::difference_type 
std::distance(_InputIterator, _InputIterator) [with _InputIterator 
= boost::geometry::model::d2::point_xy<int>]'
..\src\test.cpp:22:50:   required from here
c:\program files\mingw64\bin\../lib/gcc/x86_64-w64-  
mingw32/4.7.1/include/c++/bits/stl_iterator_base_types.h:166:53: 
error: no type named 'iterator_category' in 'class 
boost::geometry::model::d2::point_xy<int>'
c:\program files\mingw64\bin\../lib/gcc/x86_64-w64-
mingw32/4.7.1/include/c++/bits/stl_iterator_base_types.h:167:53: 
error: no type named 'value_type' in 'class   
boost::geometry::model::d2::point_xy<int>'
c:\program files\mingw64\bin\../lib/gcc/x86_64-w64- 
mingw32/4.7.1/include/c++/bits/stl_iterator_base_types.h:168:53: 
error: no type named 'difference_type' in 'class  
boost::geometry::model::d2::point_xy<int>'
c:\program files\mingw64\bin\../lib/gcc/x86_64-w64- 
mingw32/4.7.1/include/c++/bits/stl_iterator_base_types.h:169:53: 
error: no type named 'pointer' in 'class 
boost::geometry::model::d2::point_xy<int>'
c:\program files\mingw64\bin\../lib/gcc/x86_64-w64-  
mingw32/4.7.1/include/c++/bits/stl_iterator_base_types.h:170:53: 
error: no type named 'reference' in 'class 
boost::geometry::model::d2::point_xy<int>'

Answer 1

This is why you should be sparing with using-directives. You have:

using namespace std;
using namespace boost::geometry;

dragging all the names within these namespaces into the global namespace. That includes both std::distance and boost::geometry::distance and (judging from the error message) std::distance was chosen as the better overload.

If you remove using namespace std;, and qualify with std:: where necessary, then all should be fine. Alternatively, if you really want to keep the namespace pollution, then write the qualified name, boost::geometry::distance.