使用 MySQL CHAR_LENGTH() 函数的目的是什么?哪个函数是它的同义词?
mysqlmysqli database
重载运算符是具有特殊名称的函数。关键字运算符后跟所定义运算符的符号。与任何其他函数类似，重载运算符具有返回类型和参数列表。
下表显示哪些运算符可以重载，哪些不能重载 −
| Sr.No. | Operators & Description |
|---|---|
| 1 | +, -, !, ~, ++, -- These unary operators take one operand and can be overloaded. |
| 2 | +, -, *, /, % These binary operators take one operand and can be overloaded. |
| 3 | ==, !=, <, >, <=, >= The comparison operators can be overloaded. |
| 4 | &&, || The conditional logical operators cannot be overloaded directly. |
| 5 | +=, -=, *=, /=, %= The assignment operators cannot be overloaded. |
| 6 | =, ., ?:, ->, new, is, sizeof, typeof These operators cannot be overloaded. |
重载运算符定义为 −
public static Box operator+ (Box b, Box c) { }
示例
以下示例展示了如何在C# −
using System;
namespace OperatorOvlApplication {
class Box {
private double length; // Length of a box
private double breadth; // Breadth of a box
private double height; // Height of a box
public double getVolume() {
return length * breadth * height;
}
public void setLength( double len ) {
length = len;
}
public void setBreadth( double bre ) {
breadth = bre;
}
public void setHeight( double hei ) {
height = hei;
}
// Overload + operator to add two Box objects.
public static Box operator+ (Box b, Box c) {
Box box = new Box();
box.length = b.length + c.length;
box.breadth = b.breadth + c.breadth;
box.height = b.height + c.height;
return box;
}
}
class Tester {
static void Main(string[] args) {
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.setBreadth(7.0);
Box1.setHeight(5.0);
// box 2 specification
Box2.setLength(12.0);
Box2.setBreadth(13.0);
Box2.setHeight(10.0);
// volume of box 1
volume = Box1.getVolume();
Console.WriteLine("Volume of Box1 : {0}", volume);
// volume of box 2
volume = Box2.getVolume();
Console.WriteLine("Volume of Box2 : {0}", volume);
// Add two object as follows:
Box3 = Box1 + Box2;
// volume of box 3
volume = Box3.getVolume();
Console.WriteLine("Volume of Box3 : {0}", volume);
Console.ReadKey();
}
}
}
输出
Volume of Box1 : 210 Volume of Box2 : 1560 Volume of Box3 : 5400
