将long.MaxValue转换为int和将float.MaxValue转换为int有什么区别？ [英] What is the difference between casting long.MaxValue to int and casting float.MaxValue to int?

问题描述

我试图理解某些数据类型与转换之间的区别。

I'm trying to understand difference between some data types and conversion.

public static void ExplicitTypeConversion2()
    {
        long longValue=long.MaxValue;
        float floatValue = float.MaxValue;
        int integerValue = (int) longValue;
        int integerValue2 = (int)floatValue;
        Console.WriteLine(integerValue);
        Console.WriteLine(integerValue2);            
    }

当我运行该代码块时，它输出：

When I run that code block, it outputs:

-1
-2147483648

我知道，如果要分配给整数的值大于该整数可以保留的值，它将返回整数的最小值（-2147483648）。

I know that if the value you want to assign to an integer is bigger than that integer can keep, it returns the minimum value of integer (-2147483648).

据我所知， long.MaxValue 远远大于整数的最大值，但是如果我强制转换 long.MaxValue 到 int ，它返回-1。

As far as I know, long.MaxValue is much bigger than the maximum value of an integer, but if I cast long.MaxValue to int, it returns -1.

这两个强制转换有什么区别？我认为第一个也应该返回-2147483648而不是-1。

What is the difference these two casting? I think the first one also suppose to return -2147483648 instead of -1.

推荐答案

让我解释一下：

long longValue=long.MaxValue;
float floatValue = float.MaxValue;
int integerValue = (int) longValue;
int integerValue2 = (int)floatValue;

long的最大值为9,223,372,036,854,775,807或0x7FFFFFFFFFFFFFFF，因此将2的补码数减为0xFFFFFFFF后将返回0x00000001

The maximum value of long is 9,223,372,036,854,775,807 or 0x7FFFFFFFFFFFFFFF, thus 2's complement after reducing it into 0xFFFFFFFF will return 0x00000001 with minus sign bit, represented as -1 in decimal.

另一方面，float的最大值为3.40282347E + 38，因此将其强制转换为int四舍五入值设为3E + 38，并在减少后使用2的补码得到带有负号位的十六进制值0x80000000，十进制为-2147483648。

On the other side, the maximum value of float is 3.40282347E+38, thus casting it to int rounded the value to 3E+38 and using 2's complement after reducing it we get the hex value of 0x80000000 with minus sign bit, there is -2147483648 in decimal.

引用：

https://msdn.microsoft.com/zh-我们/library/system.int64.maxvalue(v=vs.110).aspx

https://msdn.microsoft.com/zh- us / library / system.single.maxvalue（v = vs.110）.aspx

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