C++ 链接器错误,未解析的外部
C++ linker errors, unresolved externals
为什么我在尝试编译此代码时遇到链接器错误,这基本上是一个模板代码 class 复杂的矩阵 & 矩阵是一个方阵,所以如果输入大小“3”表示 [3][3] 的矩阵,但不知何故它给了我错误,有帮助吗?
#include <iostream>
#include <iomanip>
using namespace std;
template <class T>
class matrix
{
private:
T** real;
T** imag;
int size;
public:
matrix(int = 0);
friend ostream& operator<<(ostream& out, matrix<T>);
};
// constructor
template <class T>
matrix<T>::matrix(int length)
{
size = length;
real = new T*[size];
for (int i = 0; i < size; i++)
real[i] = new T[size];
imag = new T*[size];
for (int i = 0; i < size; i++)
imag[i] = new T[size];
cout << "Enter real elements of matrix: ";
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
cin >> real[i][j];
cout << "Enter imag elements of matrix: ";
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
cin >> imag[i][j];
}
// functions defined here
template <class T>
ostream& operator<<(ostream& out, matrix<T> arg)
{
out << showpos;
for (int i = 0; i < arg.size; i++)
for (int j = 0; j < arg.size; j++)
out << arg.real[i][j] << arg.imag[i][j] << " ";
out << endl;
return out;
}
int main()
{
matrix <int> obj1(3);
cout << obj1;
}
因为编译器需要非模板函数。
friend ostream& operator<<(ostream& out, matrix<T>);
然而你定义为
template <class T>
ostream& operator<<(ostream& out, matrix<T> arg)
{
//some code
}
将 class 定义更改为
template<class N> friend ostream& operator<<(ostream& out, matrix<T>);
Here 是 link 到 template friend operators
的一种,它提供了有关使用模板朋友的很好的解释。
编辑 1:
根据 vsoftco 的建议,您还可以使用替代方法来定义 in-class:
class matrix{
//some code
//we don't need template here
friend ostream& operator<<(ostream& out, matrix<T>)
{
out << showpos;
for (int i = 0; i < arg.size; i++)
for (int j = 0; j < arg.size; j++)
out << arg.real[i][j] << arg.imag[i][j] << " ";
out << endl;
return out;
}
};
谢谢大家的帮助。似乎我需要模板,因为它是 class 矩阵的非成员函数,以下是正确的代码。抱歉,如果我在发布此问题时做错了什么,因为实际上这是我第一次使用堆栈溢出。
#include <iostream>
#include <iomanip>
#include <cstdlib>
using namespace std;
// Class !
template <class T> class matrix
{
private:
T** real;
T** imag;
int size;
public:
matrix(int = 0);
matrix(int,int);
template <class T> friend ostream& operator<< <T>(ostream& out, matrix<T>);
matrix operator+(matrix);
matrix operator-(matrix);
};
// Constructor !
template <class T> matrix<T>::matrix(int lenght, int dummy)
{
size = lenght;
real = new T*[size];
for (int i = 0; i < size; i++)
real[i] = new T[size];
imag = new T*[size];
for (int i = 0; i < size; i++)
imag[i] = new T[size];
}
template <class T> matrix<T>::matrix(int length)
{
size = length;
real = new T*[size];
for (int i = 0; i < size; i++)
real[i] = new T[size];
imag = new T*[size];
for (int i = 0; i < size; i++)
imag[i] = new T[size];
cout << "Enter real elements of matrix >> \n";
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
cin >> real[i][j];
cout << "Enter imag elements of matrix: >> \n";
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
cin >> imag[i][j];
}
// Main()
int main()
{
int size;
cout << "Enter Size: ";
cin >> size;
cout << "\nMatrix A created !" << endl;
matrix <int> A(size);
cout << "\nMatrix B created !" << endl;
matrix <int> B(size);
system("cls");
cout << "Matrix A" << endl;
cout << A;
cout << "\nMatrix B" << endl;
cout << B;
cout << "\nMatrix A + B" << endl;
cout << A + B;
cout << "\nMatrix A - B" << endl;
cout << A - B;
}
// Functions !
template <class T> ostream& operator<<(ostream& out, matrix<T> arg)
{
out << showpos;
for (int i = 0; i < arg.size; i++)
{
for (int j = 0; j < arg.size; j++)
{
out << arg.real[i][j] << arg.imag[i][j] << "i ";
}
out << endl;
}
return out;
}
template <class T> matrix<T> matrix<T>::operator+(matrix arg)
{
matrix<T> temp(size,0); // 0 is a inserted as dummy because I've overloaded
constructor of class
for (int i = 0; i < size; i++)
{
for (int j = 0; j < size; j++)
{
temp.real[i][j] = real[i][j] + arg.real[i][j];
temp.imag[i][j] = imag[i][j] + arg.imag[i][j];
}
}
return temp;
}
template <class T> matrix<T> matrix<T>::operator-(matrix arg)
{
matrix<T> temp(size, 0); // 0 is a inserted as dummy because I've overloaded
constructor of class
for (int i = 0; i < size; i++)
{
for (int j = 0; j < size; j++)
{
temp.real[i][j] = real[i][j] - arg.real[i][j];
temp.imag[i][j] = imag[i][j] - arg.imag[i][j];
}
}
return temp;
}
为什么我在尝试编译此代码时遇到链接器错误,这基本上是一个模板代码 class 复杂的矩阵 & 矩阵是一个方阵,所以如果输入大小“3”表示 [3][3] 的矩阵,但不知何故它给了我错误,有帮助吗?
#include <iostream>
#include <iomanip>
using namespace std;
template <class T>
class matrix
{
private:
T** real;
T** imag;
int size;
public:
matrix(int = 0);
friend ostream& operator<<(ostream& out, matrix<T>);
};
// constructor
template <class T>
matrix<T>::matrix(int length)
{
size = length;
real = new T*[size];
for (int i = 0; i < size; i++)
real[i] = new T[size];
imag = new T*[size];
for (int i = 0; i < size; i++)
imag[i] = new T[size];
cout << "Enter real elements of matrix: ";
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
cin >> real[i][j];
cout << "Enter imag elements of matrix: ";
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
cin >> imag[i][j];
}
// functions defined here
template <class T>
ostream& operator<<(ostream& out, matrix<T> arg)
{
out << showpos;
for (int i = 0; i < arg.size; i++)
for (int j = 0; j < arg.size; j++)
out << arg.real[i][j] << arg.imag[i][j] << " ";
out << endl;
return out;
}
int main()
{
matrix <int> obj1(3);
cout << obj1;
}
因为编译器需要非模板函数。
friend ostream& operator<<(ostream& out, matrix<T>);
然而你定义为
template <class T>
ostream& operator<<(ostream& out, matrix<T> arg)
{
//some code
}
将 class 定义更改为
template<class N> friend ostream& operator<<(ostream& out, matrix<T>);
Here 是 link 到 template friend operators
的一种,它提供了有关使用模板朋友的很好的解释。
编辑 1:
根据 vsoftco 的建议,您还可以使用替代方法来定义 in-class:
class matrix{
//some code
//we don't need template here
friend ostream& operator<<(ostream& out, matrix<T>)
{
out << showpos;
for (int i = 0; i < arg.size; i++)
for (int j = 0; j < arg.size; j++)
out << arg.real[i][j] << arg.imag[i][j] << " ";
out << endl;
return out;
}
};
谢谢大家的帮助。似乎我需要模板,因为它是 class 矩阵的非成员函数,以下是正确的代码。抱歉,如果我在发布此问题时做错了什么,因为实际上这是我第一次使用堆栈溢出。
#include <iostream>
#include <iomanip>
#include <cstdlib>
using namespace std;
// Class !
template <class T> class matrix
{
private:
T** real;
T** imag;
int size;
public:
matrix(int = 0);
matrix(int,int);
template <class T> friend ostream& operator<< <T>(ostream& out, matrix<T>);
matrix operator+(matrix);
matrix operator-(matrix);
};
// Constructor !
template <class T> matrix<T>::matrix(int lenght, int dummy)
{
size = lenght;
real = new T*[size];
for (int i = 0; i < size; i++)
real[i] = new T[size];
imag = new T*[size];
for (int i = 0; i < size; i++)
imag[i] = new T[size];
}
template <class T> matrix<T>::matrix(int length)
{
size = length;
real = new T*[size];
for (int i = 0; i < size; i++)
real[i] = new T[size];
imag = new T*[size];
for (int i = 0; i < size; i++)
imag[i] = new T[size];
cout << "Enter real elements of matrix >> \n";
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
cin >> real[i][j];
cout << "Enter imag elements of matrix: >> \n";
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
cin >> imag[i][j];
}
// Main()
int main()
{
int size;
cout << "Enter Size: ";
cin >> size;
cout << "\nMatrix A created !" << endl;
matrix <int> A(size);
cout << "\nMatrix B created !" << endl;
matrix <int> B(size);
system("cls");
cout << "Matrix A" << endl;
cout << A;
cout << "\nMatrix B" << endl;
cout << B;
cout << "\nMatrix A + B" << endl;
cout << A + B;
cout << "\nMatrix A - B" << endl;
cout << A - B;
}
// Functions !
template <class T> ostream& operator<<(ostream& out, matrix<T> arg)
{
out << showpos;
for (int i = 0; i < arg.size; i++)
{
for (int j = 0; j < arg.size; j++)
{
out << arg.real[i][j] << arg.imag[i][j] << "i ";
}
out << endl;
}
return out;
}
template <class T> matrix<T> matrix<T>::operator+(matrix arg)
{
matrix<T> temp(size,0); // 0 is a inserted as dummy because I've overloaded
constructor of class
for (int i = 0; i < size; i++)
{
for (int j = 0; j < size; j++)
{
temp.real[i][j] = real[i][j] + arg.real[i][j];
temp.imag[i][j] = imag[i][j] + arg.imag[i][j];
}
}
return temp;
}
template <class T> matrix<T> matrix<T>::operator-(matrix arg)
{
matrix<T> temp(size, 0); // 0 is a inserted as dummy because I've overloaded
constructor of class
for (int i = 0; i < size; i++)
{
for (int j = 0; j < size; j++)
{
temp.real[i][j] = real[i][j] - arg.real[i][j];
temp.imag[i][j] = imag[i][j] - arg.imag[i][j];
}
}
return temp;
}