C + + polymorphism (ii)--function overloading (overloading) and operator overloading

any function can be overloaded. I. Overloading of common functions

A function in C can handle only one type of data, not two or more data types; C + + uses a function with the same name to handle multiple types of data.

#include <iostream>#include<vector>using namespacestd;DoubleSqDoubleY//fun1{    returny*y;}intSqintY//fun2{    returny*y;}DoubleSqintY//Fun3{    return(Double) y*y;}voidMain () {intI=5; DoubleD=5.5; cout&LT;&LT;SQ (i) <<Endl; cout&LT;&LT;SQ (d) <<Endl;}

The fun2 and fun3 conflicts, because the parameters list of the two are the same, and the overloaded conditions are not met. If you erase FUN3, get answers 25 and 30.25.

Therefore, overloading is based on the parameter list .

Second, overloading of the constructor function

#include <iostream>using namespacestd;classa{intA, B; Public: A (); A (intIintj); ~A (); voidSet (intIintj) {a=i; b=J;}}; A::a () {A=b=0; cout<<"no_arg_cons:a="<<a<<", b="<<b<<Endl;} A::a (intIintj) {a=i; b=J; cout<<"constructor:a="<<a<<", b="<<b<<Endl;} A::~A () {cout<<"destructor:a="<<a<<", b="<<b<<Endl;}voidMain () {cout<<"Starting first round:\n"; A obja[3];  for(intI=0; i<3; i++) Obja[i]. Set (i, I+1); cout<<"Finishing First round:\n"; cout<<"starting second round:\n"; A objb[3]={a (5,6), A (7,8), A (9,Ten)}; cout<<"finishing second round.\n"; cout<<"Program being terminated!\n";}

Result:
Starting first round:no_arg_cons:a=0, b=0no_arg_cons:a=0, B=0no_arg_cons:a=0, b=0finishing first round:Starting second Round:constructor:a=5, B=6constructor:a=7, B=8constructor:a=9, b=10finishing second round. Program being terminated! Destructor:a=9, B=10destructor:a=7, b=8destructor:a=5, b=6destructor:a=2, B=3destructor:a=1, b=2destructor:a=0, b=1< /c5>

Threeoperator Overloading

In object-oriented programming languages, operators are also functions, so operators can overload them like functions to do more.

Operator overloading is implemented in two ways, one as a friend function and the other as a member function.

1. Friend function mode

#include <iostream>using namespacestd;classpoint{intx, y; Public: Point (intvx=0,intvy=0) {x=VX; Y=VY; } Friend Pointoperator+ (Point & P1, point &p2); Friend Pointoperator-(Point & P1, point &p2); voidprint () {cout<<x<<" "<<y<<Endl; }};p ointoperator+ (Point & P1, point &p2)    {point P; P.x= p1.x +p2.x; P.Y= P1.y +p2.y; returnp;} //cannot return a [local variable] referencePointoperator-(Point & P1, point &p2)    {point P; P.x= p1.x-p2.x; P.Y= P1.y-p2.y; returnp;}voidMain () {point P1 (Ten,Ten), p2 ( -, -);    P1.print (); P1= P1 + P2;//i.e. p1= operator + (p1, p2)P1.print (); P2= P1-P2;//namely p2= operator-(P1, p2)p2.print ();}

2. member function mode

#include <iostream>using namespacestd;classpoint{intx, y; Public: Point () {x=0; y =0; } Point (intVxintvy) {x= VX; y =VY;} Pointoperator+ (Point &p); Pointoperator-(Point &p); voidPrint () {cout<<x<<" "<<y<<Endl;}}; Point point::operator+ (Point &p)    {Point temp; Temp.x= x + p.x;//is temp.x = this->x + p.x;Temp.y = y +p.y; returntemp;} Point point::operator-(Point &p)    {Point temp; Temp.x= X-p.x; TEMP.Y= y-p.y; returntemp;}voidMain () {point P1 (Ten,Ten), p2 ( -, -), P3;    P3.print (); P3= P1 + P2;//i.e. P3 = P1.operator + (p2);P3.print (); P3= P3-P1;//i.e. P3 = p3.operator-(p1);p3.print ();}

25

30.25

C + + polymorphism (ii)--function overloading (overloading) and operator overloading