确实，“固定"广告与“固定"广告相反.输入/输出操纵器? [英] Really, what's the opposite of "fixed" I/O manipulator?

问题描述

这可能与此问题重复，但是我觉得它实际上没有正确回答.观察:

This may be a duplicate of this question, but I don't feel it was actually answered correctly. Observe:

#include <iostream>
#include <iomanip>
using namespace std;
int main () {
  float p = 1.00;
  cout << showpoint << setprecision(3) << p << endl;
}

输出: 1.00

现在，如果我们将该行更改为:

Now if we change that line to:

  cout << fixed << showpoint << setprecision(3) << p << endl;

我们得到: 1.000

如果我们使用固定的对立面"，我们会得到完全不同的东西:

And if we use the "opposite" of fixed we get something totally different:

  cout << scientific << showpoint << setprecision(3) << p << endl;

输出: 1.000e + 00

设置了固定后，如何返回第一个版本的行为?

How can I go back to the behaviour of the first version after fixed has been set?

推荐答案

浮点的格式规范是位掩码调用 std :: ios_base :: floatfield .在C ++ 03中，它具有两个命名设置( std :: ios_base :: fixed 和 std :: ios_base :: scientific ).默认设置是不设置这些标志.例如，可以使用

The format specification for floating points is a bitmask call std::ios_base::floatfield. In C++03 it has two named settings (std::ios_base::fixed and std::ios_base::scientific). The default setting is to have neither of these flags set. This can be achieved, e.g., using

stream.setf(std::ios_base::fmtflags(), std::ios_base::floatfield);

或

stream.unsetf(std::ios_base::floatfield);

(字段类型为 std :: ios_base :: fmtflags ).

使用当前的C ++，还有 std :: ios_base :: hexfloat ，并且添加了两个操纵器，特别是 std :: defaultfloat()可以清除 std :: ios_base :: floatfield :

With the current C++ there is also std::ios_base::hexfloat and there are two manipulators added, in particular std::defaultfloat() which clears the std::ios_base::floatfield:

stream << std::defaultfloat;

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