C++ 有重载矩阵乘法的问题“*&引用;操作人员
我想为我冗长的问题道歉,这只是我第二次使用这个网站。在不久的将来,我将确保以有序的方式综合我的问题 我正在编写一个包含重载乘法的n×m矩阵类。目前,只有当第一个输入矩阵的列与第二个矩阵的行匹配时,代码才能用于n×n和n×m矩阵的乘法,反之亦然。例如:C++ 有重载矩阵乘法的问题“*&引用;操作人员,c++,oop,c++11,matrix,C++,Oop,C++11,Matrix,我想为我冗长的问题道歉,这只是我第二次使用这个网站。在不久的将来,我将确保以有序的方式综合我的问题 我正在编写一个包含重载乘法的n×m矩阵类。目前,只有当第一个输入矩阵的列与第二个矩阵的行匹配时,代码才能用于n×n和n×m矩阵的乘法,反之亦然。例如: a1 a2 * b1 b2 这是可行的(很抱歉,我没有足够的声誉点数来发布图片,但可以将其视为1x2矩阵*2x1矩阵) 但这种类型的输入不起作用 my矩阵类由以下公式给出: #include<iostream> #in
a1 a2 * b1
b2
这是可行的(很抱歉,我没有足够的声誉点数来发布图片,但可以将其视为1x2矩阵*2x1矩阵)
但这种类型的输入不起作用
my矩阵类由以下公式给出:
#include<iostream>
#include <stdlib.h>
using namespace std;
class dymatrix
{
friend ostream & operator << (ostream &os, const dymatrix &om);
friend istream & operator >> (istream &is, dymatrix &om);
private:
int rows;
int columns;
double *matrix;
public:
dymatrix(){cout<<"Default constructor called"<<endl; columns = 0; rows=0; matrix=0;}
~dymatrix(){cout<<"Destructor called"<<endl;delete[] matrix;}
dymatrix(int inrows, int incolumns) //Parametrised objects, matrix database is defined here to store data.
{
rows = inrows;
columns = incolumns;
matrix = new double [inrows*incolumns];
for (int i=0; i<inrows*incolumns; i++)
{
matrix[i]=0;
}
}
int lengthr() const {return rows;} //Returns number of rows.
int lengthc() const {return columns;} //Return number of columns.
dymatrix &operator=( dymatrix &arr); //This is the assignment member function.
dymatrix(dymatrix&); //This is the deep copy member function.
dymatrix operator*(const dymatrix& arr)const ; //Overloading "*" operator.
double & operator[](const int n) //Overloading "[]" operator, this is important !!!
{
if(n<0 || n>=rows*columns)
{
cout<<"Error: trying to access matrix element out of bounds"<<endl;
exit(1);
}
return matrix[n];
}
int index(int j, int i) const //This member function returns the position of each index.
{
if (j > 0 && j <=rows && i > 0 && i <=columns)
{
//cout<<"i is "<<i<<" j is "<<j<<endl<<endl<<"row is "<<rows<<" columns is "<<columns<<endl;
return (i-1)+(j-1)*columns;
}
else {cout<<"Error, out of range"<<endl<<"i is "<<i<<" j is "<<j<<endl<<endl<<"row is "<<rows<<" columns is "<<columns<<endl; exit (1);}
}
double & operator()(int j, int i) const {return matrix[index(j,i)];} //The operator () returns the position of j and i in 1D array.
}; //Class End.
#包括
#包括
使用名称空间std;
类并矢矩阵
{
friend ostream&operator>(istream&is、dymatrix&om);
私人:
int行;
int列;
双*矩阵;
公众:
dymatrix(){cout在乘法运算符代码中,此行错误:
new_matrix.matrix[index(j,i)]= new_matrix.matrix[index(j,i)]+ matrix[index(j,k)]*arr(k,i);
问题是索引(j,i)
实际上是这个->索引(j,i)
,而不是新的矩阵
您应该将其替换为以下内容:
new_matrix(j,i) += matrix[index(j,k)]*arr(k,i);
但真正的问题是:有没有什么好的理由让您实现自己的矩阵类,而不是使用像Armadillo这样经过战斗测试的矩阵库?Fyidymatrix&operator=(dymatrix&arr)当赋值的右边是临时的时,它就在你的resu_a3=a1*a2;
语句中,你会不高兴。除非你使用的编译器支持对temp的非标准非常量引用(例如:MS)这不会编译。例如,这不会用clang 3.5编译。谢谢,我使用的编译器工作正常。我已将其更改为dymatrix&operator=(dymatrix arr);
但同样的问题仍然存在。哦,老兄……请帮我们大家一个忙,学会综合;如果仅仅阅读这个问题需要15分钟,你可能得不到任何帮助……我对此深表歉意,这是我第二次尝试在这个网站上提问。注意,我将学会综合我提出的任何问题不久的将来。@XiyangLiu:让index
实际执行索引可能更有意义,而不仅仅是返回索引号,这样你就可以只执行matrix.index(i,j)
而不是matrix[matrix.index(i,j)]
。有些人会使函数调用操作符过载,所以你可以执行matrix(i,j)
,但我不推荐这样做。@Matt:他有一个操作符()可以做到这一点:(*this)(I,j)
=矩阵[matrix.index(I,j)]
,这很好。在我看来,使用基于0的索引更有意义,因此循环和索引计算看起来“正常”…@MartinJ:我没有注意到。这就是当你发布太多代码时会发生的事情。。。
dymatrix dymatrix:: operator * (const dymatrix &arr) const //Overloading "*" operator.
{
if (columns != arr.rows)
{
cerr<<"SIZE DO NOT MATCH, YOU FAIL"<<endl; exit(1);
}
dymatrix new_matrix(rows,arr.columns);
for (int j = 1; j <= rows; j++)
{
for (int i = 1; i <= arr.columns; i++)
{
for (int k = 1; k <= columns; k++)
{
new_matrix.matrix[index(j,i)]= new_matrix.matrix[index(j,i)]+ matrix[index(j,k)]*arr(k,i);
cout<<"new_matrix = "<<new_matrix<<endl<<endl;
}
}
}
return new_matrix;
}
int main()
{
dymatrix a1;
cin >> a1; //Define the rows of the matrix
cout << a1<<endl<<endl;
dymatrix a2;
cin >> a2;
cout << a2<<endl<<endl;
dymatrix resu_a3;
resu_a3 = a1*a2;
cout<<"Multiplication = "<<resu_a3<<endl;
return 0;
}
#include<iostream>
#include <stdlib.h>
using namespace std;
class dymatrix
{
friend ostream & operator << (ostream &os, const dymatrix &om);
friend istream & operator >> (istream &is, dymatrix &om);
private:
int rows;
int columns;
double *matrix;
public:
dymatrix(){cout<<"Default constructor called"<<endl; columns = 0; rows=0; matrix=0;}
~dymatrix(){cout<<"Destructor called"<<endl;delete[] matrix;}
dymatrix(int inrows, int incolumns) //Parametrised objects, matrix database is defined here to store data.
{
rows = inrows;
columns = incolumns;
matrix = new double [inrows*incolumns];
for (int i=0; i<inrows*incolumns; i++)
{
matrix[i]=0;
}
}
int lengthr() const {return rows;} //Returns number of rows.
int lengthc() const {return columns;} //Return number of columns.
dymatrix &operator=( dymatrix &arr); //This is the assignment member function.
dymatrix(dymatrix&); //This is the deep copy member function.
dymatrix operator*(const dymatrix& arr)const ; //Overloading "*" operator.
double & operator[](const int n) //Overloading "[]" operator, this is important !!!
{
if(n<0 || n>=rows*columns)
{
cout<<"Error: trying to access matrix element out of bounds"<<endl;
exit(1);
}
return matrix[n];
}
int index(int j, int i) const //This member function returns the position of each index.
{
if (j > 0 && j <=rows && i > 0 && i <=columns)
{
//cout<<"i is "<<i<<" j is "<<j<<endl<<endl<<"row is "<<rows<<" columns is "<<columns<<endl;
return (i-1)+(j-1)*columns;
}
else {cout<<"Error, out of range"<<endl<<"i is "<<i<<" j is "<<j<<endl<<endl<<"row is "<<rows<<" columns is "<<columns<<endl; exit (1);}
}
double & operator()(int j, int i) const {return matrix[index(j,i)];} //The operator () returns the position of j and i in 1D array.
}; //Class End.
dymatrix::dymatrix(dymatrix &arr) //This is the copy constructor for deep copying.
{
matrix = 0; rows = arr.lengthr(); columns = arr.lengthc();
if (rows*columns >0)
{
matrix = new double [rows*columns];
for (int i =0; i < rows*columns; i++)
{
matrix[i] = arr[i];
}
}
}
dymatrix & dymatrix ::operator = (dymatrix &arr)
{
if(&arr == this) return *this; // no self assignment
delete[] matrix; matrix=0; rows=columns=0;
rows=arr.lengthr();
columns = arr.lengthc();
if(rows*columns>0)
{
matrix=new double[rows*columns];
// Copy values into new array
for(int i=0;i<rows*columns;i++) matrix[i] = arr[i];
}
return *this; // Special pointer!!
}
istream & operator >> (istream &is, dymatrix &om) //Overloading ">>" operator here to
{
cout<<"Please enter the number of rows you want"<<endl;
is >> om.rows; //Inputting number of rows.
cout<<"Enter the number of columns you want"<<endl;
is >> om.columns; //Inputting number of columns.
cout<<"Enter matrix"<<endl;
om.matrix = new double [om.rows*om.columns]; //Making a dynamic array here to put the data in.
for (int j = 1; j <= om.rows; j++)
{
for (int i = 1; i <= om.columns; i++)
{
is >> om.matrix[om.index(j,i)]; //Putting in the data into this dynamic array for each element.
}
}
return is;
}
ostream & operator << (ostream &os, const dymatrix &om) //To output the matrix in an standard matrix way
{
for(int j= 1; j<=om.rows; j++)
{
os<<endl<<endl;
for (int i = 1; i <=om.columns;i++)
{
os << om.matrix[om.index(j,i)]<<"\t"; //Similar method used in istream.
}
}
return os;
}
dymatrix dymatrix:: operator * (const dymatrix &arr) const //Overloading "*" operator.
{
if (columns != arr.rows)
{
cerr<<"SIZE DO NOT MATCH, YOU FAIL"<<endl; exit(1);
}
dymatrix new_matrix(rows,arr.columns);
for (int j = 1; j <= rows; j++)
{
for (int i = 1; i <= arr.columns; i++)
{
for (int k = 1; k <= columns; k++)
{
new_matrix.matrix[index(j,i)]= new_matrix.matrix[index(j,i)]+ matrix[index(j,k)]*arr(k,i);
cout<<"new_matrix = "<<new_matrix<<endl<<endl;
cout<<"k "<<k<<endl<<" arr.columns is "<<arr.columns<<endl<<"columns is "<<columns<<endl<<endl;
}
}
}
return new_matrix;
}
int main()
{
dymatrix a1;
cin >> a1; //Define the rows of the matrix
cout << a1<<endl<<endl;
dymatrix a2;
cin >> a2;
cout << a2<<endl<<endl;
dymatrix resu_a3;
resu_a3 = a1*a2;
cout<<"Multiplication = "<<resu_a3<<endl;
return 0;
}
new_matrix.matrix[index(j,i)]= new_matrix.matrix[index(j,i)]+ matrix[index(j,k)]*arr(k,i);
new_matrix(j,i) += matrix[index(j,k)]*arr(k,i);