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3. input

input

描述 (Description)

应用于输入流的此运算符（>>）称为提取运算符。

声明 (Declaration)

以下是std :: basic_istream :: operator >>的声明。

C++98

basic_istream& operator>> (bool& val);
basic_istream& operator>> (short& val);
basic_istream& operator>> (unsigned short& val);
basic_istream& operator>> (int& val);
basic_istream& operator>> (unsigned int& val);
basic_istream& operator>> (long& val);
basic_istream& operator>> (unsigned long& val);
basic_istream& operator>> (float& val);
basic_istream& operator>> (double& val);
basic_istream& operator>> (long double& val);
basic_istream& operator>> (void*& val);
stream buffers (2)	
basic_istream& operator>> (basic_streambuf<char_type,traits_type>* sb );
manipulators (3)	
basic_istream& operator>> (basic_istream& (*pf)(basic_istream&));
basic_istream& operator>> (
  basic_ios<char_type,traits_type>& (*pf)(basic_ios<char_type,traits_type>&));
basic_istream& operator>> (ios_base& (*pf)(ios_base&));

C++11

basic_istream& operator>> (bool& val);
basic_istream& operator>> (short& val);
basic_istream& operator>> (unsigned short& val);
basic_istream& operator>> (int& val);
basic_istream& operator>> (unsigned int& val);
basic_istream& operator>> (long& val);
basic_istream& operator>> (unsigned long& val);
basic_istream& operator>> (long long& val);
basic_istream& operator>> (unsigned long long& val);
basic_istream& operator>> (float& val);
basic_istream& operator>> (double& val);
basic_istream& operator>> (long double& val);
basic_istream& operator>> (void*& val);
stream buffers (2)	
basic_istream& operator>> (basic_streambuf<char_type,traits_type>* sb );
manipulators (3)	
basic_istream& operator>> (basic_istream& (*pf)(basic_istream&));
basic_istream& operator>> (
  basic_ios<char_type,traits_type>& (*pf)(basic_ios<char_type,traits_type>&));
basic_istream& operator>> (ios_base& (*pf)(ios_base&));

参数 (Parameters)

• val - 这是一个对象，其中存储了提取的字符所代表的值。

• sb - 指向basic_streambuf对象的指针，该对象在其受控输出序列上复制字符。

• pf - 获取并返回流对象的函数。 它通常是一个操纵器功能。

返回值 (Return Value)

返回basic_istream对象（* this）。

异常 (Exceptions)

修改val或sb指向的对象并修改流对象。

例外安全

基本保证 - 如果抛出异常，则对象处于有效状态。

例子 (Example)

在下面的示例中，对于std :: basic_istream :: operator >>

#include <iostream>     
int main () {
   int n;
   std::cout << "Enter a number: ";
   std::cin >> n;
   std::cout << "You have entered: " << n << '\n';
   std::cout << "Enter a hexadecimal number: ";
   std::cin >> std::hex >> n;         
   std::cout << "Its decimal equivalent is: " << n << '\n';
   return 0;
}

让我们编译并运行上面的程序，这将产生以下结果 -

Enter a number: 1
You have entered: 1
Enter a hexadecimal number: 5E
Its decimal equivalent is: 94