# 二元運算子過載

opBinary + 加法
opBinary - 減法
opBinary * 乘法
opBinary / 除法
opBinary % 求餘
opBinary ^^
opBinary & 按位元與
opBinary | 按位元或
opBinary ^ 按位元互斥或
opBinary << 左移
opBinary >> 右移
opBinary >>> 邏輯右移
opBinary ~ 串連
opBinary in 是否包含

```import std.stdio;

class Box
{
public:

double getVolume()
{
return length * breadth * height;
}
void setLength( double len )
{
length = len;
}

{
}

void setHeight( double hei )
{
height = hei;
}
Box opBinary(string op)(Box b)
{
if(op == "+")
{
Box box = new Box();
box.length = this.length + b.length;
box.height = this.height + b.height;
return box;
}
}
private:
double length;      // Length 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
Box box3 = new Box();    // Declare Box3 of type Box
double volume = 0.0;     // Store the volume of a box here

// box 1 specification
box1.setLength(6.0);
box1.setHeight(5.0);

// box 2 specification
box2.setLength(12.0);
box2.setHeight(10.0);

// volume of box 1
volume = box1.getVolume();
writeln("Volume of Box1 : ", volume);

// volume of box 2
volume = box2.getVolume();
writeln("Volume of Box2 : ", volume);

// Add two object as follows:
box3 = box1 + box2;

// volume of box 3
volume = box3.getVolume();
writeln("Volume of Box3 : ", volume);

}```

```Volume of Box1 : 210
Volume of Box2 : 1560
Volume of Box3 : 5400```