自己编写的一个矩阵类，个人感觉从文件中读取矩阵和将矩阵写入文件这两个函数作用大些。
收获：1. 对类的static成员函数的作用有所了解。
2. 对文件的读写操作熟练了一些。clear，seekg等
3. 对异常处理的初级应用。
下面把代码贴出来吧
//Matrix.h
//矩阵类定义
#ifndef MATRIX_H
#define MATRIX_H
#include <iostream>
#include <string>
//using namespace std; 一般头文件中使用完全限定域名字，而不是包含命名空间，防止重复包含头文件时造成的资源浪费
class Matrix
{
//从流中读入矩阵
friend std::istream& operator >> (std::istream& is, Matrix A);
//输出矩阵
friend std::ostream& operator << (std::ostream& os, const Matrix& A);
//将矩阵输出到名为str的文件中
friend void print_file(const Matrix&A,const char* str);
public:
//定义空矩阵
Matrix() {elems = NULL; row = 0; col = 0;};
//定义m*n零矩阵
Matrix(int m, int n);
//定义m*n矩阵，由a初始化
Matrix(int m, int n, double *a, int size = 0);
//复制构造函数
Matrix(const Matrix& B);
//从文件str中读取矩阵
Matrix(const char* str);
~Matrix() {delete[]elems; row = 0; col = 0; };
//重载算数操作符
Matrix& operator = (Matrix& B);
Matrix operator +(const Matrix&B)const;
Matrix operator -(const Matrix&B)const;
Matrix operator *(const Matrix&B)const;
//返回矩阵第i行第j列元素
double& operator()(int i,int j)const;
double get_row()const {return row;};
double get_col()const {return col;};
//矩阵转置
Matrix& trans()const;
protected:
private:
double* elems;
int row, col;
};
#endif 1//Matrix.cpp
2//函数实现
3
4#include "Matrix.h"
5#include <iostream>
6#include <fstream>
7#include <sstream>
8#include <string>
9#include <stdexcept>
10
11using namespace std;
12
13//重载下标操作符，返回A[i,j]
14double& Matrix::operator()(int i,int j)const
15{
16 if(i<0 || i >= row || j < 0 || j >= col)
17 throw out_of_range("The suffix is out of range");
18
19 return elems[i*col+j];
20}
21
22//从输入流中读入矩阵
23istream& operator >>(istream& is, Matrix&A)
24{
25 for(int i = 0; i != A.get_row(); ++i)
26 for(int j = 0; j != A.get_col(); ++j)
27 is >> A(i,j);
28 return is;
29}
30
31//输出矩阵
32ostream& operator <<(ostream& os, const Matrix& A)
33{
34 for(int i = 0; i != A.get_row(); ++i)
35 {
36 for(int j = 0; j != A.get_col(); ++j)
37 os << A(i,j) << " ";
38 cout <<endl;
39
}
40 cout << "------------------------" <<endl;
41
42 return os;
43
44};
45
46//将矩阵A输出到文件str中
47void print_file(const Matrix&A,const char* str)
48{
49 ofstream outfile("Matrix_out.txt",ios::app);
50 if(!outfile)
51 throw domain_error("Cannot open this file.");
52
53 for(int i = 0; i != A.row; ++i)
54 {
55 for(int j = 0; j!= A.col; ++j)
56 outfile << A(i,j);
57 outfile << endl;
58 }
59 outfile << "----------------------"<<endl;
60
61 outfile.clear();
62 outfile.close();
63}
64
65//构造m*n零矩阵
66Matrix::Matrix(int m, int n):row(m),col(n)
67{
68 if(m <1 || n <1)
69 throw out_of_range("The row or column number should be larger than 0.");
70 elems = new double[m*n];
71 for(int i = 0; i != m*n; ++i)
72 elems[i] = 0;
73}
74
75//构造m*n矩阵，从数组a中读入数据存储到矩阵中
76Matrix::Matrix(int m, int n,double* a, int size):row(m),col(n)
77{
78 if(m <0 || n<0 || size < m*n)
79 throw out_of_range("The suffix or size are out of range");
80
81 elems = new double[m*n];
82 for(int i = 0; i != m*n; ++i)
83 elems[i] = a[i];
84
85};
86
87//从文件中读入矩阵
88Matrix::Matrix(const char* str)
89{
90 //忘了刚开始的行列初始化，导致错误，寻找了半天。
91 row = 0;
92 col = 0;
93
94 ifstream infile(str,ios::in);
95 if(!infile)
96 {
97 throw domain_error("Cannot find this file.");
98 }
99
100 char ch = ' ';
101 //计算列数
102 while(infile.get(ch) && ch != '\n')
103 {
104 if(ch == ' ') ++col;
105 }
106 ++col;
107
108 //计算行数
109 infile.clear(); //在这里这个语句不必要
110 infile.seekg(0,ios::beg);//千万不能忘了重定位到文件头
111 while(infile.get(ch))
112 {
113 if(ch == '\n') ++row;
114 }
115 ++row;
116
117 infile.clear();//已经读到文件尾时想重新定位到文件头必须有这条语句
118 infile.seekg(0,ios::beg);
119
120 elems = new double[row*col];
121 int i = 0;
122 while(i != row*col)
123 infile >> elems[i++];
124
125 infile.clear();
126 infile.close();
127
128}
129
130//矩阵复制构造函数
131Matrix::Matrix(const Matrix& B):row(B.row),col(B.col)
132{
133 if((row != B.row) || (col != B.col))
134 throw invalid_argument("The Matrix should be matched.");
135
136 elems = new double[row*col];
137 for(int i = 0; i != row*col; ++i)
138 elems[i] = B.elems[i];
139
140};
141
142//重载矩阵赋值操作符
143Matrix& Matrix::operator = (Matrix& B)
144{
145
146 if((row != B.row) || (col != B.col))
147 throw invalid_argument("The matrix should be matched.");
148 row = B.row;
149 col = B.col;
150 elems = new double[row*col];
151 for(int i = 0; i != row*col; ++i)
152 elems[i] = B.elems[i];
153
154 return *this;
155};
156
157//重载矩阵相加操作符
158Matrix Matrix::operator+(const Matrix& B)const
159{
160 if((row != B.row) || (col != B.col))
161 throw invalid_argument("The matrix should be matched");
162
163 Matrix& T = * new Matrix;
164 T.row = row;
165 T.col = col;
166 T.elems = new double[row*col];
167
168 for(int i = 0; i != row*col; ++i)
169 T.elems[i] = elems[i] + B.elems[i];
170 return T;
171
172};
173
174//重载矩阵相减操作符
175Matrix Matrix::operator-(const Matrix& B)const
176{
177 if((row != B.row) || (col != B.col))
178 throw invalid_argument("The matrix should be matched");
179
180 Matrix& T = * new Matrix;
181 T.row = row;
182 T.col = col;
183 T.elems = new double[row*col];
184
185 for(int i = 0; i != row*col; ++i)
186 T.elems[i] = elems[i] - B.elems[i];
187 return T;
188
189};
190
191//重载矩阵相乘操作符
192Matrix Matrix::operator *(const Matrix& B)const
193{
194 if( col != B.row)
195 throw invalid_argument("The matrix should be matched.");
196
197 Matrix& T = *new Matrix;
198 T.row = row;
199 T.col = B.col;
200 T.elems = new double[T.row * T.col];
201
202 for(int i = 0; i != T.row; ++i)
203 for(int j = 0; j != T.col; ++j)
204 {
205 T.elems[i * T.col + j] = 0;
206 for(int k = 0; k != col; ++k)
207 T.elems[i * T.col + j] += elems[i * col + k] * B.elems[k*B.col + j];
208 }
209
210 return T;
211};
212
213//转置矩阵
214Matrix& Matrix::trans()const
215{
216 Matrix& T = *new Matrix; //new 返回的是指针，需要解引用
217 T.row = col;
218 T.col = row;
219 T.elems = new double[row*col];
220 for(int i = 0; i != T.row; ++i)
221 for(int j = 0; j != T.col; ++j)
222 T.elems[i*T.col + j] = elems[j*col + i];
223 return T;
224}
1//Mainfun.cpp
2//测试编写的矩阵类
3#include "Matrix.h"
4#include <iostream>
5#include <string>
6#include <fstream>
7#include <cstdlib>
8#include <stdexcept>
9
10using namespace std;
11
12int main()
13{
14 double d[12] = {1,2,3,4,5,6,7,8,1,2,3,4};
15 double d2[12] = {1,2,3,4,1,2,3,4,5,6,7,8};
16 Matrix A(3,4,d,12);
17 Matrix B(3,4,d2,12);
18 Matrix C= B.trans();
19
20 cout << "A = \n" << A << "B = \n" << B << "C = \n" <<C<<endl;
21 cout << "A + B \n" << A + B << "B*C \n" << B*C <<endl;
22
23 //将矩阵输出到文件Matrix_out.txt中
24 print_file(A,"Matrix_out.txt");
25
26 //从文件"Matrix_in.txt"中读取矩阵
27 Matrix D("Matrix_in.txt");
28 cout << D <<endl;
29
30 //异常处理的写起来太繁琐了，只示例一个，其他省略了。
31 try
32 {
33 Matrix D(0,3);
34 }
35 catch(out_of_range& err)
36 {
37 cerr << err.what() <<endl;
38 }
39
40 system("pause");
41 return 0;
42}
43