如何检查是否双重可以放入一个浮动无需转换到无穷远 [英] How to check if a double can fit into a float without conversion to infinity

问题描述

有没有检查一个64位浮点数可转换成32位的一个没有被转换为+/-无穷？

Is there a standard way to check if a 64 bit floating point number can be converted to a 32 bit one without being converted to +/- Infinity?

我的标准方式知道这事后能为+/-天道酬勤进行检查。

I know it can be checked afterwards for +/- Inf.

Convert.ToSingle（）将无法做到这一点

推荐答案

为了测试是否双击值 D 将转换成浮动不产生无穷，您可以测试是否 D 的绝对值严格低于双击写成 3.4028235677973366e + 38 （即 0x1.ffffffp + 127 十六进制）。这个数字是双打可以转换到浮动和那些不能之间的精确限

In order to test whether a double value d will convert to float without yielding infinity, you can test whether d's absolute value is strictly below the double written as 3.4028235677973366e+38 (that is, 0x1.ffffffp+127 in hexadecimal). This number is the exact limit between doubles that can be converted to float and those that cannot.

要扩大一点，最后有限浮动是：

To expand a little, the last finite float is:

0x1.fffffep+127   (3.4028234663852886e+38 in decimal)

什么是下一个浮动号码，如果键入浮动有更多的指数位是：

What would be the next float number if type float had more exponent bits is:

0x2.000000p+127   (3.4028236692093846e+38 in decimal)

这比后者更靠近前被向下舍入到前者的数字。该限制是两个数字的中点：

The numbers that are closer to the former than to the latter are rounded down to the former. The limit is the midpoint of the two numbers:

0x1.ffffffp+127   (3.4028235677973366e+38 in decimal)

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