C++:STL 错误 C2064
我正在尝试使用 STL,但以下内容无法编译。 main.cpp:
#include <set>
#include <algorithm>
using namespace std;
class Odp
{
public:
set<int> nums;
bool IsOdd(int i)
{
return i % 2 != 0;
}
bool fAnyOddNums()
{
set<int>::iterator iter = find_if(nums.begin(), nums.end(), &Odp::IsOdd);
return iter != nums.end();
}
};
int main()
{
Odp o;
o.nums.insert(0);
o.nums.insert(1);
o.nums.insert(2);
}
错误是:
error C2064: term does not evaluate to a function taking 1 arguments
1> c:\program files\microsoft visual studio 10.0\vc\include\algorithm(95) : see reference to function template instantiation '_InIt std::_Find_if<std::_Tree_unchecked_const_iterator<_Mytree>,_Pr>(_InIt,_InIt,_Pr)' being compiled
1> with
1> [
1> _InIt=std::_Tree_unchecked_const_iterator<std::_Tree_val<std::_Tset_traits<int,std::less<int>,std::allocator<int>,false>>>,
1> _Mytree=std::_Tree_val<std::_Tset_traits<int,std::less<int>,std::allocator<int>,false>>,
1> _Pr=bool (__thiscall Odp::* )(int)
1> ]
1> main.cpp(20) : see reference to function template instantiation '_InIt std::find_if<std::_Tree_const_iterator<_Mytree>,bool(__thiscall Odp::* )(int)>(_InIt,_InIt,_Pr)' being compiled
1> with
1> [
1> _InIt=std::_Tree_const_iterator<std::_Tree_val<std::_Tset_traits<int,std::less<int>,std::allocator<int>,false>>>,
1> _Mytree=std::_Tree_val<std::_Tset_traits<int,std::less<int>,std::allocator<int>,false>>,
1> _Pr=bool (__thiscall Odp::* )(int)
1> ]
我做错了什么?
I'm trying to use STL, but the following doesn't compile. main.cpp:
#include <set>
#include <algorithm>
using namespace std;
class Odp
{
public:
set<int> nums;
bool IsOdd(int i)
{
return i % 2 != 0;
}
bool fAnyOddNums()
{
set<int>::iterator iter = find_if(nums.begin(), nums.end(), &Odp::IsOdd);
return iter != nums.end();
}
};
int main()
{
Odp o;
o.nums.insert(0);
o.nums.insert(1);
o.nums.insert(2);
}
The error is:
error C2064: term does not evaluate to a function taking 1 arguments
1> c:\program files\microsoft visual studio 10.0\vc\include\algorithm(95) : see reference to function template instantiation '_InIt std::_Find_if<std::_Tree_unchecked_const_iterator<_Mytree>,_Pr>(_InIt,_InIt,_Pr)' being compiled
1> with
1> [
1> _InIt=std::_Tree_unchecked_const_iterator<std::_Tree_val<std::_Tset_traits<int,std::less<int>,std::allocator<int>,false>>>,
1> _Mytree=std::_Tree_val<std::_Tset_traits<int,std::less<int>,std::allocator<int>,false>>,
1> _Pr=bool (__thiscall Odp::* )(int)
1> ]
1> main.cpp(20) : see reference to function template instantiation '_InIt std::find_if<std::_Tree_const_iterator<_Mytree>,bool(__thiscall Odp::* )(int)>(_InIt,_InIt,_Pr)' being compiled
1> with
1> [
1> _InIt=std::_Tree_const_iterator<std::_Tree_val<std::_Tset_traits<int,std::less<int>,std::allocator<int>,false>>>,
1> _Mytree=std::_Tree_val<std::_Tset_traits<int,std::less<int>,std::allocator<int>,false>>,
1> _Pr=bool (__thiscall Odp::* )(int)
1> ]
What am I doing wrong?
如果你对这篇内容有疑问,欢迎到本站社区发帖提问 参与讨论,获取更多帮助,或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱,如果其他用户或者作者回复了您的评论,将不能在第一时间通知您!
发布评论
评论(3)
它需要声明为静态:
否则,您将要求
find_if
在没有实例的情况下调用实例方法。It needs to be declared static:
Otherwise, you'd be asking
find_if
to call an instance method without an instance.问题是您正在传递一个指向成员函数的指针。要调用该函数,您还需要一个指向该函数的指针,但 find_if 不允许您传递它。解决方案是使用函数对象包装它,请参阅 Boost Bind (http://www.boost.org/doc/libs/1_43_0/libs/bind/bind.html)和Boost函数(http://www.boost.org/doc/libs/1_37_0/doc/html/function.html)。
The problem is you are passing a pointer to member function. To call that function you would also need a pointer to this but the find_if doesn't let you to pass it. A solution is to wrap it using a function object, see Boost Bind (http://www.boost.org/doc/libs/1_43_0/libs/bind/bind.html) and Boost Function (http://www.boost.org/doc/libs/1_37_0/doc/html/function.html).
IsOdd
不以任何方式使用类的内部结构,因此不要将其设为成员函数。相反,将其作为一个独立的功能拉出来。然后您可以使用&IsOdd
调用find_if
。但是,更进一步将其定义为函数对象是有好处的:
然后使用
IsOdd()
调用find_if
将内联代码 在find_if
循环中,而不是取消引用函数指针并进行函数调用。IsOdd
does not use the class's internals in any way, so don't make it a member function. Instead, pull it out as a standalone function. Then you can callfind_if
with&IsOdd
.However, there is a benefit to taking things a step further and defining it as a function object:
Then calling
find_if
withIsOdd()
will inline the code within thefind_if
loop instead of dereferencing a function pointer and making a function call.