在C ++中格式化数字 [英] Formatting a number in c++

问题描述

大家好，

在代码中，当我尝试格式化数字时，显示的值为0.0.我听不懂！
在此代码中:

Hi all,

In a code, when I try to format a number, the displayed value is 0.0. I don''t understand y!
In this code :

CString FmtValues( double const& stdlat)
{
CString fmtStrStdLat, str;

fmtStrStdLat.Format(_T("%.2lf"));
  str.Format(fmtStrStdLat, stdlat);//the stdlat value is str3 0.31850513383466922,
return str;
}

但是返回值为0.0

but the return value is 0.0

推荐答案

为什么不简单地执行以下操作:

Why don''t you simply do the following:

CString FmtValues (double stdlat)
{
    CString s;
    s.Format (_T("%.21f"), stdlat);
    return s;
}

一个双精度变量按值传递，因此const是多余的.正如理查德指出的那样:应该只有一个百分号，而不是两个！

为什么是21位小数?双精度型为您提供15到17个有效的十进制数字.上面的所有内容都不过分.

A double variable is passed by value, so the const is superfluous. And as Richard pointed out: There should be only one percent sign, not two!

And why 21 decimals? The double type gives you 15 to 17 significant decimal digits. Everything above that is overkill.

Missed a "%" in the format!
Changed: fmtStrStdLat.Format(_T("%.2lf"));
To : fmtStrStdLat.Format(_T("%%.2lf")); The code displays the desired values now.

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