Matrix operator overloading

matrix.cpp

#include <string>
#include <iostream>
#include <vector>
#include <sstream>

using namespace std;
class matrix {
	private:
		vector<vector<double>> matrix_double;
	public:
		friend istream& operator>>( istream& inStream, matrix &b ) {
			//使用者輸入
			string tmp_string;
			while (getline(inStream, tmp_string)) {
				//按空白分割字串
				vector<string> results_string;
				stringstream s(tmp_string);
				while(!s.eof()) {
					string tmp;
					s >> tmp;
					if(tmp != "") results_string.push_back(tmp);
				}
				//轉為double
				vector<double> results_double;
				for(vector<string>::iterator it = results_string.begin(); it != results_string.end(); it++) {
						istringstream strStream(*it);
						double num;
						strStream >> num;
						results_double.push_back(num);
				}
				if(!results_double.empty()) b.matrix_double.push_back(results_double);
				//除錯
				if(b.matrix_double.size() > 1)
					if( b.matrix_double[b.matrix_double.size()-1].size() != b.matrix_double[b.matrix_double.size()-2].size()) {
						b.matrix_double.pop_back();
						cerr << "錯誤!!矩陣元素個數不一樣。" << endl;
						cerr << "請重新輸入：" << endl;
					}
			}
			inStream.clear();
			return inStream;
		}
		friend ostream& operator<<( ostream& outStream, matrix &b ) {
			for(unsigned int i = 0; i < b.matrix_double.size(); i++, outStream << endl)
				for(vector<double>::iterator it = b.matrix_double[i].begin(); it != b.matrix_double[i].end(); it++)
					outStream << *it << ' ';
			outStream.clear();
			return outStream;
		}
		friend matrix operator+(matrix &a, matrix &b) {
			matrix c;
			if( a.matrix_double.size() != a.matrix_double[0].size() || b.matrix_double.size() != b.matrix_double[0].size())
				cerr << "不能相加!!不為方陣。" << endl;
			else if(a.matrix_double.size() != b.matrix_double[0].size())
				cerr << "不能相加!!兩矩陣大小不一樣。" << endl;
			else {
				for(unsigned int i = 0; i < a.matrix_double.size(); i++) {
					vector<double> results_double;
					for(unsigned int j = 0; j < a.matrix_double.size(); j++) {
						results_double.push_back(a.matrix_double[i][j] + b.matrix_double[i][j]);
					}
					c.matrix_double.push_back(results_double);
				}
			}
			return c;
		}
		friend matrix operator-(matrix &a, matrix &b) {
			matrix c;
			if( a.matrix_double.size() != a.matrix_double[0].size() || b.matrix_double.size() != b.matrix_double[0].size())
				cerr << "不能相減!!不為方陣。" << endl;
			else if(a.matrix_double.size() != b.matrix_double[0].size())
				cerr << "不能相減!!兩矩陣大小不一樣。" << endl;
			else {
				for(unsigned int i = 0; i < a.matrix_double.size(); i++) {
					vector<double> results_double;
					for(unsigned int j = 0; j < a.matrix_double.size(); j++) {
						results_double.push_back(a.matrix_double[i][j] - b.matrix_double[i][j]);
					}
					c.matrix_double.push_back(results_double);
				}
			}
			return c;
		}
		friend matrix operator*(matrix &a, matrix &b) {
			matrix c;
			if(a.matrix_double[0].size() != b.matrix_double.size())
				cerr << "不能相乘!!" << endl;
			else {
				//c.matrix_double.resize(a.matrix_double.size());
				for(unsigned int i = 0; i < a.matrix_double.size(); i++) {
					vector<double> results_double(b.matrix_double[0].size());
					for(unsigned int j = 0; j < a.matrix_double[0].size(); j++)
						for(unsigned int k = 0; k < b.matrix_double[0].size(); k++)
							results_double[k] += (a.matrix_double[i][j] * b.matrix_double[j][k]);
					c.matrix_double.push_back(results_double);
				}	
			}
			return c;
		}
};

int main() {
	matrix  a, b, c;			//宣告矩陣 a, b, c
	cin >> a >> b;				//輸入矩陣 a, b
	c = a + b;		cout << c;	//輸出 a + b
	matrix d = a * b;	cout << d;	//輸出 a * b 
	matrix k = a - b;	cout << k;	//輸出 a - b
	return system("pause");
}