按值傳遞：不改變外部對象

按引用傳遞&&按地址傳遞：允許改變外部對象

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#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;

//passing by refedrence
void f(int &r)
{
??? cout << "r = " << r << endl;
??? cout << "&r = " << &r << endl;
??? r = 5 ;
??? cout << "r = " << r << endl;
}

//passing by value
void f(int a)
{
??? cout<<"a= "<<a<<endl;
??? a = 5;
??? cout << "a= " << a <<endl;
}

//passing by address
void f(int *p)
{
??? cout << "p = " << p << endl;
??? cout << "*p = " << *p << endl;
??? *p = 5;
??? cout << "p = " << p << endl;
}

int main()
{
//passing by reference
int x = 47 ;
cout << "x = " << x <<endl;
cout << "&x = " << &x << endl;
f(x);//Looks like pass-by-value
????? //is actually pass by reference
cout << "x = " << x << endl;
//output
x = 47
&x = 0x7FFF1D5C9B4C
r = 47
&r = 0x7FFF1D5C9B4C
r = 5
x = 5

//passing by address
int x = 47;
cout << "x = " << x << endl;
cout << "&x = " << &x << endl;
f(&x);
cout << "x = " << x << endl;
//output

x = 47
&x = 0x7FFF9746423c
p = 0x7FFF9746423c
*p = 47
p = 0x7FFF9746423c
x = 5


//passing by value
int x = 97 ;
cout << "x=" << x <<endl;
f(x);
cout << "x=" << x <<endl;
//output
///
x = 47
a = 47
a = 5
x = 47
}

轉載于:https://www.cnblogs.com/shaoguangleo/archive/2010/10/26/2805843.html

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