[英]C++ candidate function not viable
我尝试打印出一个空向量,但收到以下错误:
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/ostream:220:20: note: candidate function not viable: no known conversion from 'vector<int>' to 'basic_streambuf<std::basic_ostream<char>::char_type> *' (aka 'basic_streambuf<char> *') for 1st argument
basic_ostream& operator<<(basic_streambuf<char_type, traits_type>* __sb);
^
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/ostream:223:20: note: candidate function not viable: no known conversion from 'vector<int>' to 'std::nullptr_t' for 1st argument
basic_ostream& operator<<(nullptr_t)
我也尝试过std::cout << vec << std::endl;
但它仍然不起作用。
这是我的代码:
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
using namespace std;
int main() {
vector <int> vec(5);
cout << vec << endl;
return 0;
}
不要挂断无法转换为std::nullptr_t
的问题。 该错误基本上意味着您的向量类型的 output stream 运算符没有过载。 因此,您必须为向量实现自己的 output function ,如下所示:
#include <iostream>
#include <string>
#include <vector>
template<typename type_t>
std::ostream& operator<<(std::ostream& os, const std::vector<type_t>& vector)
{
bool comma = false;
for (const auto& item : vector)
{
if (comma) std::cout << ", ";
std::cout << item;
comma = true;
}
std::cout << "\n";
return os;
}
int main()
{
std::vector<int> vec{ 1,2,3,4,5 };
std::cout << vec;
return 0;
}
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