如何从浮点变量值中获取2位小数值而不舍入浮点值。 [英] How to get 2 decimal place value from a float variable value with out rounding the float value.

问题描述

假设我有一个浮点数。喜欢



float f = 123.4563434;



现在我希望float变量的值为2十进制像...一样的价值。



f = 123.45。



i想要精确的2位小数值而没有四舍五入。



如何转换123.4563434到123.45。



实际上我必须计算出准确的值。所以我在小数点后只需要2位小数。



如何实现这个？

Suppose i have a float number. like

float f=123.4563434;

now i want the value of the float variable with 2 decimal place value like.

f=123.45.

i want the exact 2 decimal place value with out the rounding.

how to convert from 123.4563434 to 123.45.

actually i have to calculate the accurate value. so i need only 2 decimal place after the decimal point.

how to achive this ?

推荐答案

你可以这样做：

You can do this:

float f = 123.4563434;
float truncatedToTwoDigits = Math.Truncate(f * 100) / 100;

将 f 乘以100后，得到 12345.63434 。如果你截断小数点后的所有内容（这就是Math.Truncate的作用），你得到 12345 。除以100，你得到 123.45 ，这是你想要的结果。



你可以做到这一点对于小数点后的任何 n 位，然后乘以除以 10 ⁿ 而不是100。

After multiplying f by 100, you get 12345.63434. If you truncate everything after the decimal point (that's what Math.Truncate does), you get 12345. By dividing that by 100, you get 123.45, which is the result you desired.

You can do this for any n digits after the decimal point, then just multiply and divide by 10ⁿ instead of 100.

您可以尝试乘以100，截断为整数值，然后除以100：

You can try to multiply by 100, truncating to integer value, and then divide-back by 100:

float f = 123.4563434f;
float temp = Math.Floor(f * 100f); // temp = 12345
float result = temp / 100f; // result = 123.45

public static float TrucatedValue(this float value) {
   return Math.Floor(value * 100f) / 100f;
}

我包含了一个扩展方法，你可以在浮点值上使用它来获得截断值。

希望这会有所帮助。

I included an extension method that you can use on float values to get the truncated value.
Hope this helps.

请注意，您在小数位后显示七位数的测试值;对于浮动/单个，你将至少丢失该数字的最后一位数，因为你超过了该格式的精确能力;请参阅：[ ^ ]和[< a href =http://stackoverflow.com/a/21688396/133321target =_ blanktitle =New Window> ^ ]。



对于种类：

Note that you show a test value with seven digits after the decimal place; for a float/single, you are going to "lose" at least the last digit of that number, since you exceed that format's precision capability; see: [^], and [^].

For variety:

private float? FloatToNPlaces(int nplaces, float f)
{
    string f1 = f.ToString("n7");
    int i = f1.IndexOf('.');
    nplaces++;

    if (i < 0 || f1.Substring(i).Length < nplaces) return null;

    return Convert.ToSingle(f1.Substring(0, f1.IndexOf('.') + nplaces));
}

// usage:
// float fx? = FloatToNPlaces(3, 4563434F); // 123.45
// float fx? = FloatToNPlaces(0, 123.4563434F); // 123.0
// float fx? = FloatToNPlaces(2, 123.0F); // 123.0

// float fx? = FloatToNPlaces(5, 123.4563434F); // null because of float limitations as described above

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