Returning Reference

A function can return a reference. In C++ programming, there are several uses for reference return values.

Example

//Returning a reference
#include <iostream.h>
double &f();
double val=100.0;
main()
{
double newval;
cout <<f()<<'$\backslash$n';// Display val's value
newval =f(); //assign value of val to newval
cout <<newval<<'$\backslash$n'; // display newval's value
f()=99.5;//change val's value
cout <<f()<<'$\backslash$n';
return 0;
}
double &f()
{
return val;// return reference to val
}

The output of this program is shown here:

100
100
99.5

At the beginning, f() is declared as returning a reference to a double and the global variable val is initialized to 100. Next the following statement displays the original value of val:

cout <<f()<<'$\backslash$n';// Display val's value

When f() is called, it returns a reference to val. Because f() is declared as returning reference, the line

return val;

automatically returns a reference to val. This reference is then used by the cout statement to display val's value.

In the line

newval=f();

The reference to val is returned by f() is used to assign the value of val to newval.

The most interesting line in the program is shown here:

f()=99.5;

This statement causes the value of val to be changed to 99.5. Since f() returns a reference to val, this reference becomes the target of the assignment statement. Thus the value 99.5 is assigned to val indirectly through the reference to it returned by f().