c++ - OpenCV，C++ : Inserting into set

Question

我正在 Ubuntu 11.04 上使用 NetBeans 6.9 开发 C++ 应用程序。我正在使用 OpenCV 2.3.1。我想知道是否有人可以告诉我这段代码有什么问题。


void AddTriangle(CvPoint buf[3], set< Triangle > &V)<br/>
{<br/>
Triangle triangle;<br/>
int inc;<br/>



<pre><code>for (inc=0; inc<3; ++inc)
{
triangle.v[inc].x=buf[inc].x;
triangle.v[inc].y=buf[inc].y;
}
V.insert((const Triangle) triangle);
</code></pre>



}


我在尝试编译时收到以下错误消息。


from /usr/include/c++/4.5/bits/locale_classes.h:42,<br/>
from /usr/include/c++/4.5/bits/ios_base.h:43,<br/>
from /usr/include/c++/4.5/ios:43,<br/>
from /usr/include/c++/4.5/istream:40,<br/>
from /usr/include/c++/4.5/sstream:39,<br/>
from /usr/include/c++/4.5/complex:47,<br/>
from /usr/local/include/opencv2/core/core.hpp:59,<br/>
from ../../OpenCV-2.3.1/include/opencv/cv.h:64,<br/>
from ../../OpenCV-2.3.1/include/opencv/cv.hpp:50,<br/>
from ../../DraculaFiles/TwoDTriangulation.cpp:12:<br/>
/usr/include/c++/4.5/bits/stl_function.h: In member function ‘bool std::less<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = sTriangle]’:<br/>
In file included from /usr/include/c++/4.5/string:50:0,
/usr/include/c++/4.5/bits/stl_tree.h:1184:4: instantiated from ‘std::pair, bool> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_unique(const _Val&) [with _Key = sTriangle, _Val = sTriangle, _KeyOfValue = std::_Identity, _Compare = std::less, _Alloc = std::allocator]’<br/>
/usr/include/c++/4.5/bits/stl_set.h:408:29: instantiated from ‘std::pair, _Compare, typename _Alloc::rebind<_Key>::other>::const_iterator, bool> std::set<_Key, _Compare, _Alloc>::insert(const value_type&) [with _Key = sTriangle, _Compare = std::less, _Alloc = std::allocator, typename std::_Rb_tree<_Key, _Key, std::_Identity<_Key>, _Compare, typename _Alloc::rebind<_Key>::other>::const_iterator = std::_Rb_tree_const_iterator, value_type = sTriangle]’


三角形定义如下。





typedef struct sTriangle<br/>
{<br/>
CvPoint v[3];<br/>
} Triangle;


如有任何帮助，我们将不胜感激，
彼得。

Answer 1

要将Triangle 放入集合中，您必须实现比较运算符。否则集合无法判断哪些值相等，哪些值不同。

typedef struct sTriangle
{
CvPoint v[3];
bool operator<(const sTriangle& other) const;
} Triangle;

bool sTriangle::operator<(const sTriangle& other) const
{
   // compare 'this' with 'other'
}

对于less操作符的实现，可以启发here .

编辑:即使不修改 sTriangle 结构，您也可以实现 less 运算符:

typedef struct sCvPoint {
int x;
int y;
} CvPoint;

typedef struct sTriangle
{
CvPoint v[3];
} Triangle;

bool operator==(CvPoint const& left, CvPoint const& right)
{
    return left.x == right.x && left.y == right.y;
}

bool operator<(CvPoint const& left, CvPoint const& right)
{
    return left.x == right.x
        ? left.y < right.y
        : left.x < right.x;
}

bool operator<(Triangle const& left, Triangle const& right)
{
    return left.v[0] == right.v[0]
        ? left.v[1] == right.v[1]
            ? left.v[2] < right.v[2]
            : left.v[1] < right.v[1]
        : left.v[0] < right.v[0];
}