我想打印我在C＃中非常小的数字在人类友好的方式，如：
30µ为3E-5或456.789n为0.000000456789 。
我知道的Humanize_number从BSD中C（）函数，但只有位整数，而不是浮点型和双兼容。 有没有在C＃中支持这些等价？
此外，应该显示数字的时候，像保持一定量的精度：
0.003596应显示为3.596µ ，不3.6µ （或者更糟， 4µ ）。
可能的答案在这里： 格式化大数与.NET但适应负LOG10是逗号后截断的数字为1个位数。 这是远远没有完成在我看来。
我想如何呈现的东西例子：
3000 3K
3300 3.3K
3333 3.333K
30000 30k
300000 300k
3000000 3M
3000003 3.000003M // or 3M if I specify "4 digits precision"
0.253 253m
0.0253 25.3m
0.00253 2.53m
-0.253003 -253.003m
我不能制定我的问题找到相关的答案在SO，因此，如果这个问题已经被回答了，火了！
试试这个：
static class Extensions
{
static string[] prefixes= { "f", "a", "p", "n", "μ", "m", string.Empty, "k", "M", "G", "T", "P", "E" };
public static string Nice(this double x, int significant_digits)
{
//Check for special numbers and non-numbers
if(double.IsInfinity(x)||double.IsNaN(x)||x==0||significant_digits<=0)
{
return x.ToString();
}
// extract sign so we deal with positive numbers only
int sign=Math.Sign(x);
x=Math.Abs(x);
// get scientific exponent, 10^3, 10^6, ...
int sci= x==0? 0 : (int)Math.Floor(Math.Log(x, 10)/3)*3;
// scale number to exponent found
x=x*Math.Pow(10, -sci);
// find number of digits to the left of the decimal
int dg= x==0? 0 : (int)Math.Floor(Math.Log(x, 10))+1;
// adjust decimals to display
int decimals=Math.Min(significant_digits-dg, 15);
// format for the decimals
string fmt=new string('0', decimals);
if(sci==0)
{
//no exponent
return string.Format("{0}{1:0."+fmt+"}",
sign<0?"-":string.Empty,
Math.Round(x, decimals));
}
// find index for prefix. every 3 of sci is a new index
int index=sci/3+6;
if(index>=0&&index<prefixes.Length)
{
// with prefix
return string.Format("{0}{1:0."+fmt+"}{2}",
sign<0?"-":string.Empty,
Math.Round(x, decimals),
prefixes[index]);
}
// with 10^exp format
return string.Format("{0}{1:0."+fmt+"}·10^{2}",
sign<0?"-":string.Empty,
Math.Round(x, decimals),
sci);
}
// test code
static void Main(string[] args)
{
double x=Math.PI/10e20;
do
{
Console.WriteLine(string.Format( "\t{0,20} = {1}", x, x.Nice(4)));
x*=10;
} while(x<=Math.PI*10e20);
}
}
测试输出有四个显著的数字：
3.14159265358979E-19 = 314.2·10^-2
1.5707963267949E-18 = 1.571f
7.85398163397448E-18 = 7.854f
3.92699081698724E-17 = 39.27f
1.96349540849362E-16 = 196.3f
9.8174770424681E-16 = 981.7f
4.90873852123405E-15 = 4.909a
2.45436926061703E-14 = 24.54a
1.22718463030851E-13 = 122.7a
6.13592315154256E-13 = 613.6a
3.06796157577128E-12 = 3.068p
1.53398078788564E-11 = 15.34p
7.6699039394282E-11 = 76.70p
3.8349519697141E-10 = 383.5p
1.91747598485705E-09 = 1.917n
9.58737992428526E-09 = 9.587n
4.79368996214263E-08 = 47.94n
2.39684498107131E-07 = 239.7n
1.19842249053566E-06 = 1.198µ
5.99211245267829E-06 = 5.992µ
2.99605622633914E-05 = 29.96µ
0.000149802811316957 = 149.8µ
0.000749014056584786 = 749.0µ
0.00374507028292393 = 3.745m
0.0187253514146196 = 18.73m
0.0936267570730982 = 93.63m
0.468133785365491 = 468.1m
2.34066892682745 = 2.341
11.7033446341373 = 11.70
58.5167231706864 = 58.52
292.583615853432 = 292.6
1462.91807926716 = 1.463k
7314.5903963358 = 7.315k
36572.951981679 = 36.57k
182864.759908395 = 182.9k
914323.799541975 = 914.3k
4571618.99770987 = 4.572M
22858094.9885494 = 22.86M
114290474.942747 = 114.3M
571452374.713734 = 571.5M
2857261873.56867 = 2.857G
14286309367.8434 = 14.29G
71431546839.2168 = 71.43G
357157734196.084 = 357.2G
1785788670980.42 = 1.786T
8928943354902.1 = 8.929T
44644716774510.5 = 44.64T
223223583872552 = 223.2T
1.11611791936276E+15 = 1.116P
5.58058959681381E+15 = 5.581P
2.79029479840691E+16 = 27.90P
1.39514739920345E+17 = 139.5P
6.97573699601726E+17 = 697.6P
3.48786849800863E+18 = 3.488E
1.74393424900432E+19 = 17.44E
8.71967124502158E+19 = 87.20E
4.35983562251079E+20 = 436.0E
2.1799178112554E+21 = 2.180·10^21
只要你想显示的数字作为标志，而不是作为一个好多0的你还可做一些这样的：
class Program
{
static void Main(string[] args)
{
//these are your "unit precedessors"
char[] exponentsbig = new char[] {' ', 'k', 'M', 'G', 'T', 'P', 'E' };
char[] exponentssmall = new char[] { ' ', 'm', 'µ', 'n', 'p', 'a', 'f' };
//some example numbers
long[] numbersBig = new long[] { 3000, 3003, 30000, 300000, 300003, 1594900000000000 };
double[] numbersSmall = new double[] { 0.0002, 0.245, 0.245003, 0.000004578 };
//some helper vars
int counter = 0;
bool edited = false;
//let's have a look at what we produce;)
string output = "";
//Big numbers incoming!!
for (int i = 0; i < numbersBig.Length; i++)
{
counter=0;
double myNumber = Convert.ToDouble(numbersBig[i]);
do
{
edited = false;
//something to prevent unnecessary unit-adding and making sure you still divide by 1000
if (myNumber/1000>1 )
{
counter++;
myNumber /= 1000;
edited = true;
}
} while (edited);
output += numbersBig[i] + " " + myNumber + exponentsbig[counter] + "\n";
}
//small numbers incoming!!
for (int i = 0; i < numbersSmall.Length; i++)
{
counter = 0;
double myNumber = numbersSmall[i];
do
{
edited = false;
//this will go to 3 digits after comma. you can make the compared smaller
//to be more exact after the comma, but keep in mind you lose steps then
if (myNumber < 1)
{
counter++;
myNumber *= 1000;
edited = true;
}
} while (edited);
output += numbersSmall[i] + " " + myNumber + exponentssmall[counter] + "\n";
}
//see what we did
Console.Write(output);
Console.ReadKey();
}
}
你可以使用的DllImport使用Humanize_Number功能？ 看到这里的细节：
动态加载在C＃中的DLL
为什么不10 ^乘（算上小数点后的数字）？ 您可以使用相同的数字算到小数点后找出要显示的单位。 这是不是导入整个库好得多。
