c++在循环中使用istream::peek检查cin的结尾

Question

我想读取一个 istream 并将其分成标记，使用 istream::peek 检查序列中的下一个字符。但是，如果不在输入末尾插入某个字符，我就无法结束循环。

有没有办法检查下一个字符是否是输入的结尾？我试过 while(c != is.eof()) 但它不起作用。

void calculator(istream& is){
  //Some structures

  char c = '0';  

  while (c != '.'){    
    c = is.peek();
    switch (c){
           //Some operations with is
           //is.ignore(1);
           //is >> variable;
    }
  }

int main (void){
   calculator (cin);
}

Answer 1

来自 std::istream::peek() 的 reference documentation它说:

Return value

If good() == true, returns the next character as obtained by rdbuf()->sgetc() Otherwise, returns Traits::eof().

所以你应该根据Traits::eof()检查返回值:

int c = 0; // Note peek() returns `int_type` actually not char
while (c != '.'){    
    c = is.peek();
    if(c == std::char_traits::eof())
    {
        break;
    }
    switch (c){
           //Some operations with is
           //is.ignore(1);
           //is >> variable;
    }
}