将float转换为double [英] Convert float to double

问题描述

我正在尝试将 Single 转换为 Double ，同时保持原始值。我发现以下方法：

I'm trying to convert Single to Double while maintaining the original value. I've found the following method:

Single f = 5.2F;
Double d1 = f; // 5.19999980926514
Double d2 = Double.Parse(f.ToString()); // 5.2 (correct)

这种做法值得推荐吗？我不需要最佳方法，但必须将预期值传递给double。

Is this practice recommendable? I don't need an optimal method, but the intended value must be passed on to the double. Are there even consequences to storing a rounded value in a double?

推荐答案

转换是精确的。所有 Single 值都可以用 Double 值表示，因为它们是用相同的方式构建的，只是具有更多可能的数字。实际上，您看到的 5.2F 是 5.1999998092651368 。如果您访问 http://www.h-schmidt.net/FloatConverter/IEEE754.html 并插入 5.2 ，您将看到它的指数为 2 ^ 2 （所以 4 ），尾数为 1.2999999523162842 。现在，如果将两个数字相乘，将得到 5.1999998092651368 。

The conversion is exact. All the Single values can be represented by a Double value, because they are "built" in the same way, just with more possible digits. What you see as 5.2F is in truth 5.1999998092651368. If you go http://www.h-schmidt.net/FloatConverter/IEEE754.html and insert 5.2 you'll see that it has an exponent of 2^2 (so 4) and a mantissa of 1.2999999523162842. Now, if you multiply the two numbers you'll get 5.1999998092651368.

单的最大精度为 7位数字，因此.NET仅显示7位数字。稍微舍入 5.1999998092651368 是 5.2

Single have a maximum precision of 7 digits, so .NET only shows 7 digits. With a little rounding 5.1999998092651368 is 5.2

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