How to add a numeric switch to a PowerShell script

Question

I know how to add switch parameters to PowerShell scripts, but the name of the switch is always a (valid) identifier like -Enable because the name is generated from the backing PowerShell variable.

[CmdletBinding()]
param(
  [switch] $Enable = $false
)

Some tools have switches like -2008. Normally, one would name the switch $2008 but this is not a valid identifier.

How can I implement such a switch as a boolean value in PowerShell? Or in other words: How to specify a different parameter name then the backing variable?

Edit 1

I wasn't aware of number only variables (which is very strange for a programming language...). Anyhow, I created that example:

function foo
{ [CmdletBinding()]
  param(
    [switch] $2008
  )
  Write-Host "2008=$2008"
}

For this code, which is accepted as valid PowerShell, I get a auto completion as wanted. But when providing that parameter, I get this error message:

foo : Es wurde kein Positionsparameter gefunden, der das Argument "-2008" akzeptiert.
In Zeile:1 Zeichen:1
+ foo -2008
+ ~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [foo], ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,foo

Translation: No positional parameter was found, that accepts the argument "-2008".

The purpose of the script is to provide translations / wrappers for command line interfaces.

Here is a set of standardized executables with parameters:

vcom.exe -2008 design.vhdl
vsim.exe -2008 design

Translation:

ghdl.exe -a --std=2008 design.vhdl
ghdl.exe -e --std=2008 design
ghdl.exe -r --std=2008 design

I would like to keep the feature of auto completion for parameters, otherwise I could process all remaining parameters and translate them by hand.

i dont understand, do you want the switch name to be exactly $true? — 4c74356b41
– 4c74356b41, Commented Sep 8, 2017 at 14:51
Normally, you would name the switch $2008 but this is not a valid identifier. So how to specify a different parameter name then the backing variable? — Paebbels
– Paebbels, Commented Sep 8, 2017 at 14:53
This can't be allowed because it creates ambiguity with parsing negative integers -- is -2008 a value for an unnamed parameter or a switch named 2008? I'm not unhappy PowerShell only allows the former. If these switches make sense in your context, consider just tweaking them so they are valid -- like -Y2008 if it's supposed to be year, -W2008 if it's supposed to enable a warning, etcetera. — Jeroen Mostert
– Jeroen Mostert, Commented Sep 8, 2017 at 15:02
funny enough, it works if you splat it so, $p=@{2008=$true}, function @p, you don't even need ${2008}, $2008 also works — 4c74356b41
– 4c74356b41, Commented Sep 8, 2017 at 15:06
@JeroenMostert of course, that makes sense. I'd probably go for a string (or string[] if values are not mutually exclusive) parameter with a limited ValidateSet attribute. You should add an answer btw — Mathias R. Jessen
– Mathias R. Jessen, Commented Sep 8, 2017 at 15:08

Sage Pourpre · Accepted Answer · 2017-09-09 15:46:51Z

1

PowerShell doesn't support numeric parameters (See this answer).

Could a validateset be an acceptable solution to your problem ?

Validate set does benefit from the autocompletion feature and this is the next best thing, in my opinion, of what you wanted.

Foo & Foos — both are the same, except Foos accept multiple parameters.

foo -std 2008
foos -std 2008,2009,2010





    function foo
{ [CmdletBinding()]
  param(
    [ValidateSet("2008",
                 "2009",
                 "2010",
                 "2011","2012")][INT]$std
  )
  Write-Host "std:$std"
}

function foos
{ [CmdletBinding()]
  param(
    [ValidateSet("2008",
                 "2009",
                 "2010",
                 "2011","2012")][INT[]]$std
  )
  $std | foreach {Write-Host "std: $_"}
}





foo -std 2008
foos -std 2008,2009,2010

answered Sep 9, 2017 at 15:46

Sage Pourpre

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3 Comments

Paebbels Over a year ago

The original program e.g. vcom does not have a -std switch in front of the version number. More over the - is missing. So I think I need to use another solution like a Python script with ArgParse.

Sage Pourpre Over a year ago

If it's a wrapper to the real exe, can't you just call it afterward using &"YourWrappedapp.exe -$std" so you are effectively using foo -std 2008 to call "YourWrappedApp.exe -2008" ? or am I missing something ?.

Paebbels Over a year ago

The wrapper (written in PowerShell) shall emulate the interface of vcom so it must provide a -2008 switch. internally it will call ghdl.exe with the switch --std=2008 if -2008 was set on the wrapper. The purpose is that existing simulator scripts for the vcom/vlib/vsim calls can be reused for the GHDL simulator, that uses a different CLI, but offers the same commands (analyze, elaborate, run simulation).

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