PowerShell和C#中存在较大的不一致

Question

根据microsoft文档，[BigInt]数据类型似乎没有定义最大值，理论上可以容纳无限大的数字，但我发现在第28位之后，开始出现一些奇怪的事情:

PS C:\Users\Neko> [BigInt]9999999999999999999999999999
9999999999999999999999999999
PS C:\Users\Neko> [BigInt]99999999999999999999999999999
99999999999999991433150857216

正如您所看到的，在第一个命令¹上，bigint按预期工作，但如果多了一个数字，在将9999999999999999999999999999999999999999991433150857216转换为9999999999991433150857216时，似乎会发生一些偏移。但是，提示符不会抛出错误，您可以继续添加更多的数字，直到第310个数字

PS C:\Users\Neko> [BigInt]99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
100000000000000001097906362944045541740492309677311846336810682903157585404911491537163328978494688899061249669721172515611590283743140088328307009198146046031271664502933027185697489699588559043338384466165001178426897626212945177628091195786707458122783970171784415105291802893207873272974885715430223118336
PS C:\Users\Neko\> [BigInt]999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999

这将引发错误

At line:1 char:318
+ ... 999999999999999999999999999999999999999999999999999999999999999999999
+                                                                          ~
The numeric constant 99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 is not valid.
    + CategoryInfo          : ParserError: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : BadNumericConstant

我认为这是一个控制台问题，而不是BigInt问题，因为该错误没有提到[BigInt]数据类型，与其他数据类型（如

PS C:\Users\Neko> [UInt64]18446744073709551615
18446744073709551615
PS C:\Users\Neko> [UInt64]18446744073709551616
Cannot convert value "18446744073709551616" to type "System.UInt64". Error: "Value was either too large or too small
for a UInt64."
At line:1 char:1
+ [UInt64]18446744073709551616
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvalidCastIConvertible

对于C#，System.Numerics.BigInt硬编码时将在第20位开始抛出错误，9999999999999999999999999999:

namespace Test
{
    class Test
    {
        static void Main()
        {
            System.Numerics.BigInteger TestInput;
            System.Numerics.BigInteger Test = 99999999999999999999;
            System.Console.WriteLine(Test);
        }
    }
}

尝试在Visual Studio中生成时，会出现以下错误

Integral constant is too large

但是，我可以向readline输入更大的数字，而不会导致错误

namespace Test
{
    class Test
    {
        static void Main()
        {
            System.Numerics.BigInteger TestInput;
            TestInput = System.Numerics.BigInteger.Parse(System.Console.ReadLine());
            System.Console.WriteLine(TestInput);
        }
    }
}

它似乎确实是无限的。 输入

999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999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工作良好²

那么，是什么原因导致了这些奇怪的[BigInt]activity呢？

¹_{，根据([char[]]“$([BigInt]999999999999999999999999999999999999999999999999)”）为28位。count}

²_{我太懒了，不愿计数数字，试图将数字解析到PowerShell中会导致错误。 据此，它是24720个字符}

Answer 1

为了补充现有的，有用的答案--特别是Pinkfloydx33的--用一个简洁的总结:

默认情况下，至少V7.0之前的所有PowerShell版本都使用[double]作为大于[decimal]::maxvalue的数字文本的数据类型，这总是会导致准确性的损失。

• 在V6.x之前（包括Windows PowerShell），避免这种情况的唯一方法是使用[bigint]::parse()，其数字表示为字符串:

[bigint]::Parse('99999999999999999999999999999')

• 在V7+中，可以使用n后缀将数字文本指定为[bigint]:

99999999999999999999999999999n  # v7+; parses as a [bigint], due to suffix 'n'

注意:可以说，考虑到PowerShell通常会自动选择适当的数字类型，在这种情况下它应该假定N，即它应该将不带后缀的

进一步阅读:

>

请参阅about_Numeric_Literals，其中显示了所有数字类型的后缀，包括它们是在什么PowerShell版本中引入的。

这个答案总结了数字文本在PowerShell中是如何解释的。

• 简言之:对于整数文本，[int]是所选择的最小类型，根据需要选择[long]或[decimal]以容纳较大的值，[double]用于[decimal]::MaxValue以外的值。

Answer 2

不幸的是，C#没有用于BigInteger的文字。 实例化BigInteger有两种方法:

1. 从基本类型（如int，long）转换（强制转换或使用构造函数）
2. 使用BigInteger.Parse分析字符串

BigInteger test = BigInteger.Parse("32439845934875938475398457938457389475983475893475389457839475");
Console.WriteLine(test.ToString());
// output: 32439845934875938475398457938457389475983475893475389457839475

查看PowerShell如何解析数字文本

Answer 3

TLDR:使用Powershell Core 7.0之前的[BigInt]::parse； 否则，请使用n后缀。

当涉及到无后缀的文字时，powershell将使用值适合的第一种类型。 整数字母的顺序是int，long，decimal，然后是double。 来自Powershell 5.1文档（bolding Mine；此段落与Powershell Core相同）:

对于没有类型后缀的整数文本:

• 如果值可以由类型[int]表示，则为其类型。
• 否则，如果值可以用类型[long]表示，则该值就是它的类型。
• 否则，如果值可以用类型[decimal]表示，则该值就是它的类型。
• 否则，它由类型[double]表示。

在您的示例中，该值超过了Decimal.MaxValue的值，因此默认情况下，您的文本是Double文本。 该double值不能精确表示，它被“转换”为最接近的可表示的double值。

$h = [double]99999999999999999999999999999
"{0:G29}“ -f $h

产出

99999999999999991000000000000

显然那不是确切的数字，只是一个字符串形式的表示。 但它能让你知道发生了什么。 现在我们取这个不精确的double值，并将其强制转换为biginteger。 原始精度损失会被转换运算符转移并叠加。 这就是Powershell中实际发生的情况（请注意bigint):

$h = [BigInt][double]99999999999999999999999999999
"{0:G}“ -f $h

产出

99999999999999991433150857216

[这实际上是最接近于表示的double值。如果您可以（使用内置工具）打印第一个示例中double的实际值，则它将打印此值。]

当您添加额外的额外数字时，您将超过一个数字文本的最大值，因此您收到的另一个异常。

现在请注意，与Powershell不同的是，C#默认情况下使用整数，这就是为什么出现异常的数字要少得多的原因。 在C#中添加d后缀会给您提供更大的范围。 下面的操作很好，将是一个double。

var h = 99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999D;

再增加一个数字将引发以下错误:

错误CS0594:浮点常量超出“double”类型的范围

请注意，在Powershell中，d后缀用于decimal文字，而不用于double。 doubles没有显式后缀（假定为默认值）

回到原来的问题，如果您使用的是Windows Powershell或Powershell Core<=V6.2，则需要使用BigInteger.Parse:

[bigint]::Parse("99999999999999999999999999999") 

产出:

99999999999999999999999999999

Powershell Core 6.2为整数类型引入了许多新的文字后缀，例如无符号，short和byte。 最后，Powershell Core 7.0为bigint引入了n后缀，这意味着您现在可以这样做:

99999999999999999999999999999n 

产出:

99999999999999999999999999999

有关Powershell Core中可用后缀的详细信息，请参阅文档。

正如评论中所指出的，另一个可行的选择是用引号括住字面。

[bigint]'99999999999999999999999999999' 

产出

99999999999999999999999999999

不管看起来如何，这并不是[bigint]::new([string])的速记。 相反，这是一种确保文本不被视为double，而是被视为具有许多数字的整数文本，即所谓的“大值文本”的方法。 请参阅此部分的文档。

如果尝试[bigint]::new('literal')，Powershell会识别出您打算将该值用作文本。 现在需要注意的是，没有接受另一个bigint的bigint的构造函数。 但是，有一个构造函数采用double。 我们的超大型文本将以bigint开头，然后Powershell将其隐式转换为double（失去精度），然后将其作为最佳匹配传递给[bigint]::new([double])，再次给出不正确的结果:

[bigint]::new('99999999999999999999999999999') 

产出:

99999999999999991433150857216