C++/Overload/Inserter

An inserter can be used to output data in any form

<source lang="cpp">

1. include <iostream>

using namespace std; class MyClass {

 int x, y;

public:

 MyClass(int i, int j) { 
    x=i; 
    y=j; 
 }
 friend ostream &operator<<(ostream &stream, MyClass o);

}; ostream &operator<<(ostream &stream, MyClass o) {

 register int i, j;
 for(i=0; i<o.x; i++)
   stream << "*";
 stream << "\n";
 for(j=1; j<o.y-1; j++) {
   for(i=0; i<o.x; i++)
     if(i==0 || i==o.x-1) stream << "*";
     else stream << " ";
   stream << "\n";
 }
 for(i=0; i<o.x; i++)
    stream << "*";
 stream << "\n";
 return stream;

} int main() {

 MyClass a(14, 6), b(30, 7), c(40, 5);
 cout << "Here are some:\n";
 cout << a << b << c;
 return 0;

}

      </source>

Create a non-friend inserter.

<source lang="cpp">

1. include <iostream>

using namespace std; class MyClass { public:

 int x, y;  // must be public
 MyClass() { 
    x = 0; 
    y = 0; 
 }
 MyClass(int i, int j) { 
    x = i; 
    y = j; 
 }

}; // An inserter for the MyClass class. ostream &operator<<(ostream &stream, MyClass ob) {

 stream << ob.x << ", " << ob.y << "\n";
 return stream;

} int main() {

 MyClass a(1, 1), b(10, 23);
 cout << a << b;
 return 0;

}

      </source>

Output account info to a file using an inserter.

<source lang="cpp">

1. include <iostream>
2. include <fstream>
3. include <cstring>

using namespace std; class account {

 int custnum;
 char name[80];
 double balance;

public:

 account(int c, char *n, double b) 
 {
   custnum = c;
   strcpy(name, n);
   balance = b;
 }
 friend ostream &operator<<(ostream &stream, account ob);

}; ostream &operator<<(ostream &stream, account ob) {

 stream << ob.custnum << " ";
 stream << ob.name << " " << ob.balance;
 stream << "\n";
 return stream;

} int main() {

 account  Rex(1011, "Joe", 12323.34);
 ofstream out("accounts", ios::out | ios::binary);
 if(!out) {
   cout << "Cannot open output file.\n";
   return 1;
 }
 out << Rex;
 out.close();
 return 0;

}

      </source>

PhoneNumber inserter function

<source lang="cpp">

1. include <iostream>
2. include <cstring>

using namespace std; class PhoneNumber { public:

 char name[80];
 int areaCode;
 int prefix;
 int num;
 PhoneNumber(char *n, int a, int p, int nm){
   strcpy(name, n);
   areaCode = a;
   prefix = p;
   num = nm;
 }

}; // Display name and phone number. ostream &operator<<(ostream &stream, PhoneNumber o) {

 stream << o.name << " ";
 stream << "(" << o.areaCode << ") ";
 stream << o.prefix << "-" << o.num << "\n";
 return stream; // must return stream

} int main() {

 PhoneNumber a("T", 111, 555, 1234);
 PhoneNumber b("A", 312, 555, 5768);
 PhoneNumber c("T", 212, 555, 9991);
 cout << a << b << c;
 return 0;

}

      </source>

This program draws right triangles

<source lang="cpp">

1. include <iostream>

using namespace std; class triangle {

 int height, base;

public:

 triangle(int h, int b) { height = h; base = b; }
 friend ostream &operator<<(ostream &stream, triangle ob);

}; // Draw a triangle. ostream &operator<<(ostream &stream, triangle ob) {

 int i, j, h, k;
 i = j = ob.base-1;
 for(h=ob.height-1; h; h--) {
   for(k=i; k; k--) 
     stream << " ";
   stream << "*";
   
   if(j!=i) {
     for(k=j-i-1; k; k--)
       stream << " ";
     stream << "*";
   }
   i--;
   stream << "\n";
 }
 for(k=0; k<ob.base; k++) stream << "*";
 stream << "\n";
 return stream;

} int main() {

 triangle t1(5, 5), t2(10, 10), t3(12, 12);
 cout << t1;
 cout << endl << t2 << endl << t3;
 return 0;

}

      </source>

Use a friend inserter for objects of type MyClass.

<source lang="cpp">

1. include <iostream>

using namespace std; class MyClass {

 int x, y;

public:

 MyClass() { 
    x = 0; 
    y = 0; 
 }
 MyClass(int i, int j) { 
    x = i; 
    y = j; 
 }
 friend ostream &operator<<(ostream &stream, MyClass ob);

}; ostream &operator<<(ostream &stream, MyClass ob) {

 stream << ob.x << ", " << ob.y << "\n";
 return stream;

} int main() {

 MyClass a(1, 1), b(10, 23);
 cout << a << b;
 return 0;

}

      </source>

Use friend function to operator: <<, >>

>" src="http://www.java2s.com/Code/CppImages/Usefriendfunctiontooperator.PNG">

<source lang="cpp">

1. include <iostream>

using namespace std; class factor {

 int num;   // number
 int lfact; // lowest factor

public:

 factor(int i);
 friend ostream &operator<<(ostream &stream, factor ob);
 friend istream &operator>>(istream &stream, factor &ob);

}; factor::factor(int i) {

 int n;
 num = i;
 for(n=2; n < (i/2); n++)
   if(!(i%n)) break;
 if(n<(i/2)) lfact = n;
 else lfact = 1;

} istream &operator>>(istream &stream, factor &ob) {

 stream >> ob.num;
 int n;
 for(n=2; n < (ob.num/2); n++)
   if(!(ob.num%n)) break;
 if(n < (ob.num/2)) 
    ob.lfact = n;
 else 
 ob.lfact = 1;
 return stream;

} ostream &operator<<(ostream &stream, factor ob) {

 stream << ob.lfact << " is lowest factor of ";
 stream << ob.num << "\n";
 return stream;

} int main() {

 factor o(32);
 cout << o;
 cin >> o;
 cout << o;
 return 0;

}

      </source>