Well this is my first experience with lambda, and I know I might be misusing this feature but I'm wondering why should I get a compile error?
这是我第一次使用lambda,我知道我可能会误用这个功能,但我想知道为什么我会遇到编译错误?
GameMap::MoveDirection AIPlayer::getSafeRouteTo(const GameMap::PlayerInfo& s, const Point& e)
{
struct node : public Point
{
GameMap::MoveDirection parent;
float d;
node():Point(){};
node(Point p) : Point(p)
{
};
};
auto lambdaFunction = [this,&e](node&left,node&right)->bool
{
return this->getDistance(left,e) + left.d < this->getDistance(right,e) + right.d;
};
priority_queue<node,vector<node>, decltype(lambdaFunction)> Q;
//do stuff
return GameMap::MD_None;
}
and for the sake of argument let me say that MoveDirection is an enum, and Point does have a default constructor. as I commented by removing that specific line I don't get the error but I really need it to be there. here are the errors VC2010 is generating:
为了说明,让我说MoveDirection是一个枚举,而Point确实有一个默认的构造函数。正如我通过删除该特定行评论我没有得到错误,但我真的需要它在那里。以下是VC2010产生的错误:
d:\program files (x86)\microsoft visual studio 10.0\vc\include\queue(225): error C2512: '`anonymous-namespace'::<lambda0>' : no appropriate default constructor available
1> d:\program files (x86)\microsoft visual studio 10.0\vc\include\queue(223) : while compiling class template member function 'std::priority_queue<_Ty,_Container,_Pr>::priority_queue(void)'
1> with
1> [
1> _Ty=AIPlayer::getSafeRouteTo::node,
1> _Container=std::vector<AIPlayer::getSafeRouteTo::node>,
1> _Pr=`anonymous-namespace'::<lambda0>
1> ]
1> c:\users\ali\documents\visual studio 2010\projects\bokhorbokhor\aiplayer.cpp(147) : see reference to class template instantiation 'std::priority_queue<_Ty,_Container,_Pr>' being compiled
1> with
1> [
1> _Ty=AIPlayer::getSafeRouteTo::node,
1> _Container=std::vector<AIPlayer::getSafeRouteTo::node>,
1> _Pr=`anonymous-namespace'::<lambda0>
1> ]
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
1 个解决方案
#1
4
The lambda is not default constructible. You have to pass it to this constructor of the priority_queue
:
lambda不是默认的可构造的。您必须将它传递给priority_queue的此构造函数:
explicit priority_queue(const Compare& x = Compare(), Container&& = Container());
Like this:
priority_queue<node,vector<node>, decltype(lambdaFunction)> Q ( lambdaFunction );
#1
4
The lambda is not default constructible. You have to pass it to this constructor of the priority_queue
:
lambda不是默认的可构造的。您必须将它传递给priority_queue的此构造函数:
explicit priority_queue(const Compare& x = Compare(), Container&& = Container());
Like this:
priority_queue<node,vector<node>, decltype(lambdaFunction)> Q ( lambdaFunction );