PowerShell 减法是否在内部将 uint32 值转换为 int32？

发布于 2024-10-27 04:10:58 字数 229 浏览 0 评论 0原文

当我想编写涉及两个 [unit32] 变量的减法脚本时，我收到警告“错误：“对于 Int32 来说值太大或太小。”

一个示例来说明我所看到的情况

$v1 = [uint32]([int32]::MaxValue + 1)
$v2 = [uint32]([int32]::MaxValue + 2)
$v2 - $v1

这是正常行为吗？我怎样才能避免这个错误？

原文

When I wanted to script a subtraction involving two [unit32] variables I got the warning "Error: "Value was either too large or too small for an Int32."

A sample to illustrate what I saw

$v1 = [uint32]([int32]::MaxValue + 1)
$v2 = [uint32]([int32]::MaxValue + 2)
$v2 - $v1

Is this normal behaviour ?
And how can I avoid the error ?

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梦里人 2024-11-03 04:10:58

你是对的，这有点奇怪。但正确的写法如下，并且有效：

PS C:\> $v1 = [uint32]([int32]::MaxValue) + 1
PS C:\> $v2 = [uint32]([int32]::MaxValue) + 2
PS C:\> $v2 -$v1
1

解释是 ([int32]::MaxValue + 1) 是没有意义的。如果你分解你的第一个情感，你会发现它变成了双重情感。

PS C:\> $a = ([int32]::MaxValue + 1)
PS C:\> $a.gettype()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Double                                   System.ValueType

真正奇怪的是，如果你只添加一行，它就会再次起作用。

PS C:\> $v1 = [uint32]([int32]::MaxValue + 1)
PS C:\> $v2 = [uint32]([int32]::MaxValue + 2)
PS C:\> $v2 += 1
PS C:\> $v2 - $v1
2

您可以使用 Cmdlet Trace-Command 研究此类表达式：

PS C:\> Trace-Command -Name TypeConversion -Expression {[uint32]([int32]::MaxValue + 1)} -PSHost
DÉBOGUER : TypeConversion Information: 0 : Converting "64" to "System.Int32".
DÉBOGUER : TypeConversion Information: 0 :     Result type is assignable from value to convert's type
DÉBOGUER : TypeConversion Information: 0 : Converting "System.Object[]" to "System.Object[]".
DÉBOGUER : TypeConversion Information: 0 :     Result type is assignable from value to convert's type
DÉBOGUER : TypeConversion Information: 0 : Conversion to System.Type
DÉBOGUER : TypeConversion Information: 0 :     Conversion to System.Type
DÉBOGUER : TypeConversion Information: 0 :         Found "System.Int32" in the loaded assemblies.
DÉBOGUER : TypeConversion Information: 0 : Converting "2147483647" to "System.Double".
DÉBOGUER : TypeConversion Information: 0 :     Numeric conversion succeeded.
DÉBOGUER : TypeConversion Information: 0 : Converting "1" to "System.Double".
DÉBOGUER : TypeConversion Information: 0 :     Numeric conversion succeeded.
DÉBOGUER : TypeConversion Information: 0 : Conversion to System.Type
DÉBOGUER : TypeConversion Information: 0 :     Conversion to System.Type
DÉBOGUER : TypeConversion Information: 0 :         Found "System.UInt32" in the loaded assemblies.
DÉBOGUER : TypeConversion Information: 0 : Converting "2147483648" to "System.UInt32".
DÉBOGUER : TypeConversion Information: 0 :     Numeric conversion succeeded.
2147483648

大多数情况下 Trace-Command 会提供更多信息。

太平绅士

You are right it's a bit strange. But the correct way of writting it, is the following and it works :

PS C:\> $v1 = [uint32]([int32]::MaxValue) + 1
PS C:\> $v2 = [uint32]([int32]::MaxValue) + 2
PS C:\> $v2 -$v1
1

The explanation is that ([int32]::MaxValue + 1) is non sense. If you decompose your first affectation you can see a conversion into a double.

PS C:\> $a = ([int32]::MaxValue + 1)
PS C:\> $a.gettype()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Double                                   System.ValueType

The really strange thing is that if you just add a line it works again.

PS C:\> $v1 = [uint32]([int32]::MaxValue + 1)
PS C:\> $v2 = [uint32]([int32]::MaxValue + 2)
PS C:\> $v2 += 1
PS C:\> $v2 - $v1
2

You can investigate such expression with the Cmdlet Trace-Command:

PS C:\> Trace-Command -Name TypeConversion -Expression {[uint32]([int32]::MaxValue + 1)} -PSHost
DÉBOGUER : TypeConversion Information: 0 : Converting "64" to "System.Int32".
DÉBOGUER : TypeConversion Information: 0 :     Result type is assignable from value to convert's type
DÉBOGUER : TypeConversion Information: 0 : Converting "System.Object[]" to "System.Object[]".
DÉBOGUER : TypeConversion Information: 0 :     Result type is assignable from value to convert's type
DÉBOGUER : TypeConversion Information: 0 : Conversion to System.Type
DÉBOGUER : TypeConversion Information: 0 :     Conversion to System.Type
DÉBOGUER : TypeConversion Information: 0 :         Found "System.Int32" in the loaded assemblies.
DÉBOGUER : TypeConversion Information: 0 : Converting "2147483647" to "System.Double".
DÉBOGUER : TypeConversion Information: 0 :     Numeric conversion succeeded.
DÉBOGUER : TypeConversion Information: 0 : Converting "1" to "System.Double".
DÉBOGUER : TypeConversion Information: 0 :     Numeric conversion succeeded.
DÉBOGUER : TypeConversion Information: 0 : Conversion to System.Type
DÉBOGUER : TypeConversion Information: 0 :     Conversion to System.Type
DÉBOGUER : TypeConversion Information: 0 :         Found "System.UInt32" in the loaded assemblies.
DÉBOGUER : TypeConversion Information: 0 : Converting "2147483648" to "System.UInt32".
DÉBOGUER : TypeConversion Information: 0 :     Numeric conversion succeeded.
2147483648

Most of the time Trace-Command give more informations.

回复收藏 0 原文

明媚殇 2024-11-03 04:10:58

显然，PowerShell 的算术总是有符号的，并且确实在必要时不会转换为下一个更大的类型。作为解决方法，您可以使用 [long]/[Int64]：

PS> [long]$v2-$v1
1

或者最初将变量声明为 [long]。

Apparently PowerShell's arithmetic is always signed and does not convert into the next larger type if necessary, indeed. As a workaround you can use [long]/[Int64]: