# Unary Operators Overloading

The following table shows the list of unary operators and its purpose.

Function Name Operator Purpose
opUnary - Negative of (numeric complement of)
opUnary + The same value as (or, a copy of)
opUnary ~ Bitwise negation
opUnary * Access to what it points to
opUnary ++ Increment
opUnary -- Decrement

An example is shown below which explains how to overload an binary operator.

```import std.stdio;

class Box {
public:
double getVolume() {
return length * breadth * height;
}

void setLength( double len ) {
length = len;
}

void setBreadth( double bre ) {
breadth = bre;
}

void setHeight( double hei ) {
height = hei;
}

Box opUnary(string op)() {
if(op == "++") {
Box box = new Box();
box.length = this.length + 1;
box.breadth = this.breadth + 1 ;
box.height = this.height + 1;
return box;
}
}

private:
double length;      // Length of a box
double breadth;     // Breadth of a box
double height;      // Height of a box
};

// Main function for the program
void main( ) {
Box Box1 = new Box();    // Declare Box1 of type Box
Box Box2 = new Box();    // Declare Box2 of type Box
double volume = 0.0;     // Store the volume of a box here

// box 1 specification
Box1.setLength(6.0);
Box1.setBreadth(7.0);
Box1.setHeight(5.0);

// volume of box 1
volume = Box1.getVolume();
writeln("Volume of Box1 : ", volume);

// Add two object as follows:
Box2 = ++Box1;

// volume of box2
volume = Box2.getVolume();
writeln("Volume of Box2 : ", volume);
}
```

When the above code is compiled and executed, it produces the following result −

```Volume of Box1 : 210
Volume of Box2 : 336
```
d_programming_overloading.htm
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