下表显示了一元运算符，其目的列表。
| 函数名称 | 运算符 | 目的 |
|---|---|---|
| opUnary | - | 负数(数字补) |
| opUnary | + | 相同值(或者，副本) |
| opUnary | ~ | 按位取反 |
| opUnary | * | 访问指向 |
| opUnary | ++ | 自增 |
| opUnary | -- | 自减 |
一个例子如下，解释如何重载一个二元运算符。
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);
}
让我们编译和运行上面的程序，这将产生以下结果：
Volume of Box1 : 210 Volume of Box2 : 336
