📜  C++中的is_reference模板

📅  最后修改于: 2021-05-30 13:28:25             🧑  作者: Mango

C++ STL的std :: is_reference模板用于检查类型是否为引用类型。它返回一个显示相同值的布尔值。

语法

template  struct is_reference;

参数:此模板接受单个参数T(特质类),以检查T是否为引用类型。

返回值:此模板返回一个布尔值,如下所示:

  • True :如果类型是引用类型。
  • False :如果类型是非引用类型。

下面的程序说明了C++ STL中的std :: is_reference模板:

程序1

// C++ program to illustrate
// std::is_reference template
  
#include 
#include 
using namespace std;
  
// main program
class gfg {
};
  
int main()
{
    cout << boolalpha;
    cout << "is_reference: "
         << '\n';
    cout << "gfg: "
         << is_reference::value
         << '\n';
    cout << "gfg&: "
         << is_reference::value
         << '\n';
    cout << "gfg&&: "
         << is_reference::value
         << '\n';
  
    return 0;
}
输出:
is_reference: 
gfg: false
gfg&: true
gfg&&: true

程序2

// C++ program to illustrate
// std::is_reference template
  
#include 
#include 
using namespace std;
  
// main program
int main()
{
    cout << boolalpha;
    cout << "is_reference: "
         << '\n';
    cout << "int: "
         << is_reference::value
         << '\n';
    cout << "int&: "
         << is_reference::value
         << '\n';
    cout << "int&&: "
         << is_reference::value
         << '\n';
    cout << "char: "
         << is_reference::value
         << '\n';
    cout << "char&: "
         << is_reference::value
         << '\n';
    cout << "char&&: "
         << is_reference::value
         << '\n';
  
    return 0;
}
输出:
is_reference: 
int: false
int&: true
int&&: true
char: false
char&: true
char&&: true

程序3

// C++ program to illustrate
// std::is_reference template
  
#include 
#include 
using namespace std;
  
// main program
int main()
{
  
    cout << boolalpha;
    cout << "is_reference: "
         << '\n';
    cout << "float: "
         << is_reference::value
         << '\n';
    cout << "float&: "
         << is_reference::value
         << '\n';
    cout << "float&&: "
         << is_reference::value
         << '\n';
    cout << "double: "
         << is_reference::value
         << '\n';
    cout << "double&: "
         << is_reference::value
         << '\n';
    cout << "double&&: "
         << is_reference::value
         << '\n';
  
    return 0;
}
输出:
is_reference: 
float: false
float&: true
float&&: true
double: false
double&: true
double&&: true
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