C++/Function/Function Parameters

Demonstrates the use of return values with reference type.

<source lang="cpp">

1. include <iostream>
2. include <string>

using namespace std;

double& referenceMin( double&, double&);

int main() {

  double x1 = 3.1,  x2 = x1 + 10.5,  y;
  y = referenceMin( x1, x2);   
  cout << "x1 = " << x1 << "     "
       << "x2 = " << x2 << endl;
  cout << "Minimum: " << y  << endl;
  ++referenceMin( x1, x2);     
  cout << "x1 = " << x1 << "     "      
       << "x2 = " << x2 << endl;        
  ++referenceMin( x1, x2);           
                              
  cout << "x1 = " << x1 << "     "      
       << "x2 = " << x2 << endl;        
  referenceMin( x1, x2) = 10.1;       
                                
  cout << "x1 = " << x1 << "     "    
       << "x2 = " << x2 << endl;      
  referenceMin( x1, x2) += 5.0;      
  cout << "x1 = " << x1 << "     "     
       << "x2 = " << x2 << endl;       
  return 0;

} double& referenceMin( double& a, double& b){

   return a <= b ? a : b;       

}

      </source>

Expressions with reference type exemplified by string assignments.

<source lang="cpp">

1. include <iostream>
2. include <string>
3. include <cctype>

using namespace std; void strToUpper( string& ); int main(){

  string text("Test with assignments \n");
  strToUpper(text);
  cout << text << endl;
  strToUpper( text = "lower case");
  cout << text << endl;
  strToUpper( text += " and lower case!\n");
  cout << text << endl;
  return 0;

} void strToUpper( string& str){

   int len = str.length();
   for( int i=0; i < len; ++i)
     str[i] = toupper( str[i]);

}

      </source>

Function parameters

<source lang="cpp">

1. include <iostream>
2. include <string>

using namespace std; void printMessage(string, int); int main () {

  string name;
  int age; 
  cout << "Enter name: ";
  cin >> name;
  cout << "Enter age: ";
  cin >> age;
  printMessage(name, age); 
  return 0;

} void printMessage (string theName, int theAge) {

  cout << "Your name is " << theName 
     << " and your age is " << theAge << endl;

}

      </source>

Function: reference version and pointer version

<source lang="cpp">

1. include <iostream>

using namespace std; void referenceVersion(int &i); // reference version void pointerVersion(int *i); // pointer version int main() {

 int i = 10;
 int j = 20;
 referenceVersion(i);
 pointerVersion(&j);
 cout << i << " " << j << "\n";
 return 0;

} // using a reference parameter void referenceVersion(int &i) {

 i = -i;

} // using a pointer parameter void pointerVersion(int *i) {

 *i = - *i;

}

      </source>

Function uses two arguments

<source lang="cpp">

1. include <iostream>
2. include <string>

using namespace std; void printMessage(string, string); int main () {

  string name1, name2;
  cout << "Enter first name: ";
  cin >> name1;
  cout << "Enter last name: ";
  cin >> name2;
  printMessage(name1, name2); 
  return 0;

} void printMessage (string firstName, string lastName) {

  cout << "Your name is " << firstName << " " << lastName << endl;

}

      </source>

Passed by value and passed by reference

<source lang="cpp">

1. include <iostream>

using namespace std; void addNumbers(int, int, int&); int main () {

  int firstNum, secondNum, sum = 0;
  cout << "Enter first number: ";
  cin >> firstNum;
  cout << "Enter second number: ";
  cin >> secondNum;
  addNumbers (firstNum, secondNum, sum);
  cout << firstNum << " + " << secondNum << " = " << sum;
  return 0;

} void addNumbers (int x, int y, int& z) {

  z = x + y;

}

      </source>

Passes the variable to be doubled by reference

<source lang="cpp">

1. include <iostream>

using namespace std; void doubleIt(int&); int main () {

  int num;
  cout << "Enter number: ";
  cin >> num;
  doubleIt(num);
  cout << "The number doubled in main is " << num << endl;
  return 0;

}

void doubleIt (int& x) {

  cout << "The number to be doubled is " << x << endl;
  x *= 2;
  cout << "The number doubled in doubleIt is " << x << endl;

}

      </source>

Passing Arguments by Reference

<source lang="cpp">

1. include <iostream>

using namespace std; void doubleIt(int); int main () {

  int num;
  cout << "Enter number: ";
  cin >> num;
  doubleIt(num);
  cout << "The number doubled in main is " << num << endl;
  return 0;

} void doubleIt (int x) {

  cout << "The number to be doubled is " << x << endl;
  x *= 2;
  cout << "The number doubled in doubleIt is " << x << endl;

}

      </source>

Passing Arguments by Value

<source lang="cpp">

1. include <iostream>
2. include <string>

using namespace std; void printMessage(string); int main () {

  string str;
  cout << "Enter a string: ";
  cin >> str;
  printMessage(str); 
  return 0;

} void printMessage (string s) {

  cout << "You inputted " << s;

}

      </source>

Pass string (char *) into a function

<source lang="cpp">

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

using namespace std; void center(char *s); int main() {

 center("www.java2s.com");
 center("www.java2s.com");
 return 0;

} void center(char *s) {

 int len;
 len = 40+(strlen(s)/2);
 cout << setw(len) << s << "\n";

}

      </source>