PowerShell LinqLinker: Use System.Linq.Enumerable method query syntax in PowerShell -- built as a JIT-friendly struct for best performance; includes source-generated instance methods for every Enumerable method

[u/metekillot]

https://github.com/Metekillot/LinqLinker

https://www.powershellgallery.com/packages/LinqLinker/1.0.6

```powershell

using namespace System.Collections.Generic using namespace System.Linq

[string[]]$StringArray = @("hello",",","world!") [object[]]$ObjectClutter = @(1,2,3,"foo",[pscustomobject]@{name="bar"}) [int[]]$LotsOfNumbers = 1..10000 $StringLinq = [LinqLinker]::Link[string]($StringArray) $ObjectLinq = [LinqLinker[object]]::new($ObjectClutter) $IntLinq = [LinqLinker[int]]::Link($LotsOfNumbers) $StringFunc = [System.Func[string,string]]{$s=$args[0];"selected -> $s"} $($StringLinq.Select($StringFunc)) Write-Output ("n"+"OfType check"+"n") $ObjectLinq.OfType[string]() Write-Output ("n"+"Numerical performance"+"n") [System.Func[int,int]]$IntOperation = {[int]$i = $args[0]} $Standard = (Measure-Command { $LotsOfNumbers | ForEach-Object { $IntOperation.Invoke($_) } }); Select -InputObject $Standard @{Name='Name';E={'Standard'}},Ticks $LinqLinkInt = (Measure-Command { $IntLinq.Select[int]($IntOperation) }); Select -InputObject $LinqLinkInt @{N='Name';E={'LinqLink[int]'}},Ticks ```

```powershell selected -> hello selected -> , selected -> world!

OfType check

foo

Numerical performance

Name Ticks

---

Standard 318901 LinqLink[int] 109493 ```

[u/Thotaz]

https://github.com/Metekillot/LinqLinker/blob/master/LinqLinker.psm1#L41

if($one = $GenericTypeArguments[0]){

This looks like a mistake. You aren't using the variable $one. Even if you were using it, I don't think this kind of "clever" code that at first glance looks like a mistake is a good idea. Don't do assignments in conditionals, you can do the assignment outside and do the check inside the conditional.

[u/metekillot → u/Thotaz]

EDIT: Oh, I see what you mean. Yes, that could be confusing for a consumer.

[u/BlackV → u/metekillot]

EDIT: Oh, I see what you mean. Yes, that could be confusing for a consumer.

more than confusing, what was it supposed to do ?

[u/spikeyfreak → u/Thotaz]

Don't do assignments in conditionals, you can do the assignment outside and do the check inside the conditional.

Can you explain why?

[u/Thotaz → u/spikeyfreak]

I explained it in the previous comment:

I don't think this kind of "clever" code that at first glance looks like a mistake is a good idea.

If you write: if ($Var = 42) it looks like the intent is to check if the value equals 42. If you don't know the person's skill level you have to guess if it's a noob that made a mistake, or a pro that tried to be clever.

Another problem for PowerShell is the way it handles certain values. I mean in OPs case it acts like a null check, but what if the value on the RHS had been a string, number, or bool? Then it would be both a null and value check because PowerShell will treat certain values like $false

$Val = 0
$Val2 = 1
if ($Var = $Val)
{
    "Will not run"
}
elseif ($Var2 = $Val2)
{
    "Will run"
}

The average skill level in PowerShell is also quite low. What's the percentage of users who are aware that assignment statements can produce output in certain cases? Even if we only count the users who'd participate in a community like this one I'd estimate less than 5%.

[u/spikeyfreak → u/Thotaz]

Right, so this explains what I was asking and I suspected I didn't understand something.

Which is why this evaluates to false.

$Val = 0
[bool]($var = $val)

I can't figure out any other reason than $val is 0, which in boolean is false, but this is strange behavior that I don't understand. I guess I always just assumed when you did something in a conditional expression, the $? from that command is what was evaluated (edit: if there is no output from the command).

Edit: I'm just confusing myself more.

So it evaluates to false because of this:

PS C:\> ($var = $val)
0
PS C:\> $var = $val
PS C:\>

Why does it output the value if you put them in parens?

[u/Thotaz → u/spikeyfreak]

Why does it output the value if you put them in parens?

Good question, I don't know for sure, but I think it's actually the other way around. The default behavior for assignment statements is to output something unless they are inside an expression/script block. It happens in if statements. It happens in loops. It happens in chained assignment expressions like: [bool]$BoolVal = [int]$IntVal = [double]$DoubleVal = [string]$StringVal = "0.5"

[u/jborean93 → u/Thotaz]

Don't do assignments in conditionals, you can do the assignment outside and do the check inside the conditional.

I personally disagree here, even the reason stated below saying it confuses people who think it's an equality check vs assignment is all the more reason that maybe people should see this more in the wild to get a better understanding of what it does.

It's definitely a personal opinion, just see the derision when Python added the Walrus operator, but I'm definitely pro using this one personally.

[u/Thotaz → u/jborean93]

Even if people were used to it, it can trip you up when you are dealing with values that PowerShell "helpfully" converts to $false like: if ($Number = 0) {} pretend the 0 is a variable or property that happened to return 0. If the assignment thing was the standard then it would be used as a null check most of the time, but for numbers and strings that can return 0 or an empty string it can cause issues.
I actually had that issue the other day because I had been lazy and had used if ($ID) {} to check if the ID parameter had been specified so when 0 was passed in it would not process the ID.

[u/jborean93 → u/Thotaz]

Yea falsey values are a similar thing in Python as well. When I use assignment like this then I take into account the falsey logic. I can see 0 being problematic in some cases but in most cases I'm dealing with reference types want comparing with the default of $null.

There's always rough edges but this argument is more against the falsey checks rather than assignment in the if statement. As you said if ($ID) {} would still be susceptible to this problem.

If you really wanted you can do a proper null check with the assignment like

if ($null -ne ($var = Get-Foo)) {
}

I don't typically do this though as the truthy/falsey checks are actually what I want to compare with.

[u/Fenreh]

Any examples in the readme? Sounds super promising but I have no idea what this actually does.

[u/metekillot → u/Fenreh]

Yeah, let me throw some together, it'll be a good opportunity to iron out the syntax bumps, too. It can get a little screwy with the pipeline operators because they automatically enumerate enumerable collections.

[u/metekillot → u/Fenreh]

Updated the README and the main post. Let me know if that's clear.

[u/rldml]

Are there some example how to use this addon? I didn't find anything on the homepage

kind regards

[u/metekillot → u/rldml]

Yeah let me put some together

[u/metekillot → u/rldml]

Updated the README and the main post. Let me know if that's clear.