C++ std::make_signed用法及代碼示例

<type_traits>頭文件中提供了C++ STL的std::make_signed模板。 C++ STL的std::make_signed模板用於通過保留任何cv-qualifiers來獲取與T(Triat類)相對應的帶符號類型。可以使用std::is_same::value函數檢查給定類型T是否為帶符號類型。

頭文件：

#include<type_traits>

模板類別：

template< class T >
struct make_signed;

template<class T>
using make_signed_t 
    = typename make_signed<T>::type;

用法:

std::make_signed<T>::type

參數：模板std::make_signed接受單個參數T(Trait類)，並將類型T設為有符號類型。

下麵是在C++中演示std::make_signed的程序：

程序：

// C++ program to illustrate 
// std::make_signed 
// make_signed 
#include <iostream> 
#include <type_traits> 
using namespace std; 
  
// Declare enum 
enum ENUM1 { a, 
             b, 
             c }; 
  
enum class ENUM2:unsigned char { x, 
                                   y, 
                                   z }; 
  
// Driver Code 
int main() 
{ 
  
    // Declare variable using make_signed 
    // for int, unsigned, const unsigned, 
    // enum1 and enum2 
    typedef make_signed<int>::type A; 
    typedef make_signed<unsigned>::type B; 
    typedef make_signed<const unsigned>::type C; 
    typedef make_signed<ENUM1>::type D; 
    typedef make_signed<ENUM2>::type E; 
  
    cout << boolalpha; 
  
    // Check if the above declared variables 
    // are signed type or not 
    cout << "A is signed type? "
         << is_same<int, A>::value 
         << endl; 
  
    cout << "B is signed type? "
         << is_same<int, B>::value 
         << endl; 
  
    cout << "C is signed type? "
         << is_same<int, C>::value 
         << endl; 
  
    cout << "D is signed type? "
         << is_same<int, D>::value 
         << endl; 
  
    cout << "E is signed type? "
         << is_same<int, E>::value 
         << endl; 
  
    return 0; 
}

輸出：

A is signed type? true
B is signed type? true
C is signed type? false
D is signed type? true
E is signed type? false

參考： http://www.cplusplus.com/reference/type_traits/make_signed/

相關用法

注：本文由純淨天空篩選整理自bansal_rtk_大神的英文原創作品 std::make_signed in C++ with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。