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C Entry series (31) -- operator overloading

2022-07-26 08:42:00 【InfoQ】

Overload operator

Is a function with a special name , It's through keywords operator Defined by the symbol followed by the operator . Like other functions , Overloaded operators have return types and parameter lists .

General syntax format ：

// Modifier   return type  operator  Overloadable operators （ parameter list ）
public static Student operator +(Student a, Student b)
{
 // Method body ;
}

Operator overloading is actually function overloading . First, call the corresponding operator function through the specified operation expression , Then convert the operation object into the argument of the operator function , Then determine the overload of the function to be called according to the type of the argument , This process is done by the compiler .

Overloadable and non overloadable operators

C# Require pairwise overloading of comparison operators . If overloaded ==, Must also be overloaded !=, Otherwise, a compilation error will occur . meanwhile , The comparison operator must return bool Type value , This is the fundamental difference from other arithmetic operators .

Code example

Next, reload “+” Operator , For example ：（ heavy load “+” The compiler will automatically reload “+=”）;

using System;

namespace _6_2_1 Operator overloading 
{
 class Program
 {
 static void Main(string[] args)
 {
 Student st1 = new Student();
 Student st2 = new Student();
 Student st3 = new Student();

 st1._acore = 40;
 st2._acore = 50;

 Console.WriteLine(&quot;st1 and st2 Whether the results are the same :&quot; + (st1 == st2));
 Console.WriteLine(&quot;st1 and st2 Whether the results are the same :&quot; + (st1 != st2));

 Console.WriteLine(&quot; Performance before calculation ：{0},{1},{2}&quot;, st1._acore, st2._acore, st3._acore);

 // Add objects 
 st3 = st1 + st2;
 // The compiler automatically reloads +=
 st1 += st2;

 Console.WriteLine(&quot; Result after calculation ：{0},{1},{2}&quot;,st1._acore,st2._acore,st3._acore);
 

 Console.ReadKey();
 }
 

 }

 class Student
 {
 private int acore;

 public int _acore {
 get { return acore; }
 set { acore = value; }
 }

 //+ heavy load ：  Object addition , Get student grades and 
 public static Student operator +(Student b, Student c)
 {
 Student stu = new Student();
 stu.acore = b.acore + c.acore;

 return stu;
 }

 // When overloading == when , Must overload ！=, Otherwise, compile and report an error 
 public static bool operator ==(Student b , Student c)
 {
 bool result = false;
 if(b.acore == c.acore)
 {
 result = true;
 }
 return result;
 }

 public static bool operator !=(Student b, Student c)
 {
 bool result = false;
 if (b.acore != c.acore)
 {
 result = true;
 }
 return result;
 }


 }
}