call of overloaded 'xxx' is ambiguous
这里定义了一个模版函数，功能同STL里的copy函数：
#include <vector>
#include <list>
#include <iostream>
template <typename Iter1, typename Iter2>
Iter2 copy(Iter1 f1, Iter1 e1, Iter2 f2)
{
for (f1; f1 != e1; ++f1, ++f2)
{
*f1 = *f2;
}
return f2;
}
int main()
{
int arr[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
std::vector<int> vec{1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
copy(arr, arr + 10, vec.begin());
return 0;
}
编译时报了call of overloaded 'copy(int [10], int*, std::vector<int>::iterator)' is ambiguous错误。
c:\Source\drill.cpp: In function 'int main()':
c:\Source\drill.cpp:27:36: error: call of overloaded 'copy(int [10], int*, std::vector<int>::iterator)' is ambiguous
copy(arr, arr + 10, vec.begin());
^
c:\Source\drill.cpp:6:7: note: candidate: Iter2 copy(Iter1, Iter1, Iter2) [with Iter1 = int*; Iter2 = __gnu_cxx::__normal_iterator<int*, std::vector<int> >]
Iter2 copy(Iter1 f1, Iter1 e1, Iter2 f2)
^~~~
In file included from C:/mingw-w64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/vector:60:0,
from c:\Source\drill.cpp:1:
C:/mingw-w64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/stl_algobase.h:446:5: note: candidate: _OI std::copy(_II, _II, _OI) [with _II = int*; _OI = __gnu_cxx::__normal_iterator<int*, std::vector<int> >]
copy(_II __first, _II __last, _OI __result)
从报错信息可以看出，编译器匹配到了stl_algobase.h里的copy函数，因为我传的参数std::vector::iterator(vec.begin())是属于namespace std的。
解决的办法一：指定命名空间
#include <vector>
#include <list>
#include <iostream>
namespace LK
{
template <typename Iter1, typename Iter2>
Iter2 copy(Iter1 f1, Iter1 e1, Iter2 f2)
{
for (f1; f1 != e1; ++f1, ++f2)
{
*f1 = *f2;
}
return f2;
}
}
int main()
{
int arr[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
std::vector<int> vec{1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
LK::copy(arr, arr + 10, vec.begin());
return 0;
}
解决的办法二：函数名用括号包住
#include <vector>
#include <list>
#include <iostream>
template <typename Iter1, typename Iter2>
Iter2 copy(Iter1 f1, Iter1 e1, Iter2 f2)
{
for (f1; f1 != e1; ++f1, ++f2)
{
*f1 = *f2;
}
return f2;
}
int main()
{
int arr[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
std::vector<int> vec{1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
(copy)(arr, arr + 10, vec.begin());
return 0;
}
参考资料
