用带std :: cout的零正确填充负整数 [英] Correctly pad negative integers with zeros with std::cout

问题描述

我发现这个问题已经问了，但是每个人给出的答案是

I found this question already asked, but the answer everybody gives is

std::cout << std::setw(5) << std::setfill('0') << value << std::endl;

这是对正数的罚款，但是-5，它打印：

which is fine for positive numbers, but with -5, it prints:

000-5

有没有办法让它打印-0005或强制cout总是打印至少5位数（这将导致-00005），我们可以做printf？

Is there a way to make it print -0005 or to force cout to always print at least 5 digits (which would result in -00005) as we can do with printf?

推荐答案

std::cout << std::setw(5) << std::setfill('0') << std::internal << -5 << '\n';
//                                                     ^^^^^^^^

输出：

-0005

std :: internal

编辑：

对于那些关心这些事情的人，N3337（〜c ++ 11 ）， 22.4.2.2.2 ：

For those those that care about such things, N3337 (~c++11), 22.4.2.2.2:

The location of any padding is determined according to Table 91.
                  Table 91 - Fill padding
State                               Location
adjustfield == ios_base::left       pad after
adjustfield == ios_base::right      pad before
adjustfield == internal and a
sign occurs in the representation   pad after the sign
adjustfield == internal and
representation after stage 1 began
with 0x or 0X                       pad after x or X
otherwise                           pad before

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