C / C++ / MFC

• constructors are the very basics of an OOP language (you must be sure to grasp them before even attempting to code).
• accessing an otherwise unaccessible member is the very purpose of the friend declaration.
  

Tarun Jha wrote:

as in the above code i have converted class Polar to class Rectangle,

Rectangle& Rectangle::operator =(const Polar& polar)

#include <iostream>
#include <cmath>
using namespace std;

class Polar;

//====================================================
class Rectangle
{
  float length, bredth;
public:
  Rectangle(){}
  Rectangle(float ,float);

  operator Polar();

  int getLength(){return(length);}
  int getBredth(){return(bredth);}
  void putLength(float x){length = x;}
  void putBredth(float y){bredth = y;}

  void putData(){cout<<"Length : "<<length<<"\tBreadth : "<<bredth<<endl;}
  ~Rectangle(){}
};


//====================================================

class Polar{
  float angle, rad;
public:

  Polar(){}
  Polar(float , float);

  operator Rectangle();

  int getAngle(){return(angle);}
  int getRadius(){return(rad);}
  void putAngle(float a){angle=a;}
  void putRadius(float r){rad = r;}

  void putData(){cout<<"Angle : "<<angle<<"\tRadius : "<<rad<<endl;}
  ~Polar(){}
};

//===========================================================
Rectangle::Rectangle(float x, float y)
{
  length = x;
  bredth = y;
}

Rectangle::operator Polar()
{
  Polar temp;
  float a = atan2(bredth, length), r = sqrt(length*length + bredth*bredth);
  temp.putAngle(a);
  temp.putRadius(r);

  return(temp);
}

//===========================================================
Polar::Polar(float x, float y)
{
  angle = x;
  rad = y;
}
Polar::operator Rectangle()
{
  Rectangle temp;
  float l = rad*cos(angle), b =rad*sin(angle);
  temp.putLength(l);
  temp.putBredth(b);
  return(temp);
}

//===========================================================
int main()
{
  float radians = 120 * M_PI / 180; // convert to radians

  // roundtrip polar->rectangle->polar
  Polar p1(radians, 25);
  p1.putData();

  Rectangle r1 = p1;
  r1.putData();

  Polar p2 = r1;
  p2.putData();

  return 0;
}

Quote:

So basically i want to add 2 matrix object and assign the result to the third non-initiated matrix object, without changing the values of first 2 original matrix.

Quote:

Enter matrix elements row by row

m[0][0] = 1
m[0][1] = 2
m[1][0] = 3
m[1][1] = 4
m[2][0] = 5
m[2][1] = 6


1 2
3 4
5 6
m[0][0] = 7
m[0][1] = 8
m[1][0] = 9
m[1][1] = 10
m[2][0] = 11
m[2][1] = 12


7 8
9 10
11 12




8 10 47120720 0 0 0 0 0 0 0 50331651 41272 47127056 0 47120720 0 0 2396 136 0
12 14 47120720 0 1550742898 1148219457 1549890657 1633906508 1700027500
1426092141 1146242387 1229016399 1162100046 1330924371 1429482832 844253517 1398079566 1329877573 1313423693 1095717471
16 18 47120720 0 1162690894 1918981181 1426091637 1347568979 1229344594
1128088908 1934974010 1551069797 1970430292 1398145134 1127232561 1414417743 1397509967 1547322173 1735357008 544039282
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
47120720 0 47127424 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

#include <iostream>
using namespace std;

class matrix{
    int **p;                        //pointer to Matrix
    int d1, d2;
    int id=0;                        //identif which operator is used

public:
    //matrix(){}                      //default constructor
    matrix(int x=20, int y=20);       //parameterised

    //to pass private data-members to other objects
    int getD_1(){return (d1);}
    int getD_2(){return (d2);}
    //int getId(const int x){id =x ;}
    //void showId(){cout<<"ID :\t"<<id<<endl;}

    //for taking input nad printing output
    void get_element();
    void put_element();

    //to check feasibility
    friend int checkAdd(matrix &, matrix &);                                     //to check the feasibility of the operation
    friend int checkMul(matrix &, matrix &);

    //Rule of three
    friend matrix operator+(matrix &, matrix &);
    friend matrix operator*(matrix &, matrix &);
    //friend matrix operator-(matrix &, matrix &);

    void operator = (matrix );

    ~matrix(){
        for (int i = 0; i < d1; i++)
            delete p[i];
        delete p;
    }
};

//=================================================================================================================

//defining overloaded assingment operator
void matrix::operator = (matrix obj){
    this->d1 = obj.d1;
    this->d2 = obj.d2;
    this->id = obj.id;
    for(int i=0; i<d1; i++)
        for(int j=0; j<d2; j++)
            this->p[i][j] = obj.p[i][j];
}

//defining overloaded addition operator
matrix operator+(matrix &a, matrix &b){
    matrix temp;
    temp.d1 = a.d1;
    temp.d2 = a.d2;
    temp.id = 1;

    if(checkAdd(a, b) == 0){                //checks the viability if it's feasible or not.
        for(int i=0; i<temp.d1; i++)
            for(int j=0; j<temp.d2; j++)
                temp.p[i][j] = a.p[i][j] + b.p[i][j] ;

        return(temp);
    }
    else {
        cout<<"Matrix addition not possible as rows and coloumn's of given 2 matrices are not equal"<<endl;
        return(a);
    }
}

//defining overloaded Multiplication operator
matrix operator*(matrix &a, matrix &b){
    matrix temp;
    temp.d1 = a.d1;
    temp.d2 = b.d2;
    temp.id = 2;

    if(checkMul(a, b) == 0){              //checks the viability if it's feasible or not.
        int sum=0;
        for (int c = 0; c < a.d1; c++) {
            for (int d = 0; d < b.d2; d++) {
                for (int k = 0; k <b.d1; k++) {
                    sum = sum + a.p[c][k]*b.p[k][d];
                }
                temp.p[c][d] = sum;
                sum = 0;
            }
        }
        return (temp);
    }
    else {
        cout<<"Matrix Multiplication is not possible as coloumn of 1st Matrix != Row of 2nd Matrix "<<endl;
        return(a);
    }
}

//defining parameterised constucter
matrix ::matrix(int x, int y){
    d1 = x;
    d2 = y;
    p = new int *[d1];                  //creates an array of pointers

    for(int i=0; i<d1; i++)
        p[i] = new int [d2];            //creates row for each row
}

//defining checkAdd f^n to check if given 2 matrices obj can be added or not
int checkAdd(matrix &a, matrix &b){
    if(a.getD_1() == b.getD_1() && a.getD_2() == b.getD_2())
        return 0;
    else return 1;
}

//defining checkMul f^n to check if 2 matrices obj can be Multiplied.
int checkMul(matrix &a, matrix &b){
    if(a.getD_2() == b.getD_1())
        return 0;
    else return 1;
}

//gets the element from the user.
void matrix::get_element(){
    for(int i=0; i<d1; i++)
        for(int j=0; j<d2; j++){
            cout<<"m["<<(i+1)<<"]["<<(j+1)<<"] = ";
            cin>>p[i][j];
        }
}


//displays the current matrix
void matrix::put_element(){
    if(id == 1) cout<<"\nThe result of addition of 2 matrices is :"<<endl;
    else if(id==2)  cout<<"\nThe result of product of 2 matrices is:"<<endl;

    for(int i=0; i<d1; i++){
        for(int j=0; j<d2; j++){
            cout<<p[i][j]<<"\t";
        }
        cout<<endl;
    }
    cout<<"\n";
}

//=====================================================================================================================

int main(){
    matrix A(3, 2), B(2, 4), C;                     //matrix objects a constucted

    cout<<"Enter matrix elements row by row \n\n";
    A.get_element();
    A.put_element();

    B.get_element();
    B.put_element();

    C = A * B;
    C.showId();
    C.put_element();

    C = A + B;
    C.showId();
    C.put_element();

    return 0;
}

1. Use the existing I2C support on the Raspberry Pi with the I2C GPIO pins
   
2. Implement your own I2C support on general use GPIO pins
   

Quote:

all of the sample codes I have read so far are "limited" to open ioctl file and "write " to I2C slave address.

int fd = open("/dev/i2c-1", O_RDWR);
// Use I2C_SLAVE_FORCE if the device is in use (e.g. when a driver is installed)
ioctl(fd, I2C_SLAVE, addr);
read(fd, buffer, length);

dtoverlay=i2c-speed,i2c1_baudrate=400000

dtparam=i2c_vc=on

#include <bcm2835.h>  

int main(int argc, char **argv)  
{  
    char buf[1];

    if (!bcm2835_init())return 1;  
    bcm2835_i2c_begin();                //Start I2C operations.
    bcm2835_i2c_setSlaveAddress(0x20);  //I2C address
    bcm2835_i2c_set_baudrate(10000);    //1M baudrate

    while(1)  
    {   
        buf[0] = 0xEF;    //LED ON
        bcm2835_i2c_write(buf,1);
        bcm2835_delay(500);
        buf[0] = 0xFF;     //LED OFF
        bcm2835_i2c_write(buf,1);
        bcm2835_delay(500); 
    }    
    bcm2835_i2c_end();  
    bcm2835_close();  
    return 0;  
}