std :: cout :: setf不起作用（setf为hex）(std::cout::setf doesn't work (setf to hex))

std :: cout :: setf不起作用（setf为hex）(std::cout::setf doesn't work (setf to hex))

我在“Practical C ++ Programming”一书中测试了代码。 但以下示例并不像书中所说的那样有效。 我错过了什么？ 请帮忙。

#include <iostream> int main() { int number = 0x3FF; std::cout << "Dec: " << number << '\n'; std::cout.setf(std::ios::hex); std::cout << "Hex: " << number << '\n'; std::cout.setf(std::ios::dec); }

预期的结果是

Dec: 1023 Hex: 3ff

但是，我得到了

Dec: 1023 Dec: 1023

I tested code in the book "Practical C++ Programming". But following example doesn't work as book says. What am I missing? Please help.

#include <iostream> int main() { int number = 0x3FF; std::cout << "Dec: " << number << '\n'; std::cout.setf(std::ios::hex); std::cout << "Hex: " << number << '\n'; std::cout.setf(std::ios::dec); }

The expected result was

Dec: 1023 Hex: 3ff

But, I got

Dec: 1023 Dec: 1023

最满意答案

你需要使用setf的第二个重载来清除std::ios::basefield掩码的基本标志：

std::cout.setf(std::ios::hex, std::ios::basefield); Dec: 1023 Hex: 3ff

在ideone上演示。

You need to use the second overload of setf that clears base flags with the std::ios::basefield mask:

std::cout.setf(std::ios::hex, std::ios::basefield); Dec: 1023 Hex: 3ff

Demo on ideone.