DIY: Ternary operator

leedesmond’s blog » Blog Archive » Ternary operator ?:

leedesmond’s blog » Blog Archive » Ternary operator ?: — Sun, 31 Dec 2006 00:44:53 GMT

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re: DYI: Ternary operator

Nick Howell — Sun, 31 Dec 2006 03:39:25 GMT

Made a few modifications for myself, and also added ?? (the coalescence operator):

<pre>

filter Invoke-Ternary ($Predicate, $Then, $Otherwise = $null)

{

if($predicate -is [scriptblock]) { $predicate = &$predicate }

if ($predicate) {

if($then -is [ScriptBlock]) { &$then }

else { $then }

} elseif($otherwise) {

if($otherwise -is [ScriptBlock]) { &$otherwise }

else { $otherwise }

}

filter Invoke-Coalescence($predicate, $alternative) {

if($predicate -is [scriptblock]) { $predicate = &$predicate }

Invoke-Ternary $predicate $predicate $alternative

}

set-alias ?: Invoke-Ternary -Option AllScope

set-alias ?? Invoke-Coalescence -Option AllScope

</pre>

re: DYI: Ternary operator

keith_hill — Tue, 02 Jan 2007 11:28:20 GMT

FYI thew equivalent of your Invoke-Coalescence is already in PSCX and is aliased to ?? e.g.:

$logdir = ?? {$env:logdir} {'C:\Temp'}

Again if PoSH supported this natively the syntax could be nicer:

$logdir = $env:logdir ?? 'c:\Temp'

Although we call the function rather lamely Inovke-NullAlt. Mind if we steal this name for PSCX? :-) BTW, this is a nice equivalent of the KornShell "Foo = ${paramaeter:-word}" functionality.

re: DYI: Ternary operator

monkeypecker — Fri, 05 Jan 2007 01:13:37 GMT

FYI DYI != DIY

ttfn

-mp

re: DIY: Ternary operator

Nick Howell — Sat, 06 Jan 2007 09:22:10 GMT

Keith, feel free. If you want to be really picky, you might want to call it Invoke-NullCoalescence (which is probably the most accurate term for it).

I'm now considering something like this:

filter Invoke-NullCoalescenceMethod($Object, $Method, [array]$Parameters = @()) {

?: $Object {$item = $Object.PsObject.Members.Item($Method); if($item.Invoke) { $item.Invoke($Parameters) } elseif($item.get_Value -and $Parameters) { $item.Value = $Parameters } else { $item.Value }} $null;

}

Set-Alias ?. Invoke-NullCoalescenceMethod

It should work for getters, setters, and methods.

This is sortof like the null-drilldown offered in Cω (C-omega). It would be really super-fantastic if we could get some of these things in the language. I *really* like the idea of having this: $x?.StartInfo?.CreateNoWindow ?= $true;

That would just be handy.

Powershell Refactored. – Introduction and Invoke Ternary.

Powershell Refactored — Fri, 20 Apr 2007 10:39:52 GMT

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Re: Ternary conditional operator

Latest Newsgroup Posts — Tue, 18 Sep 2007 16:52:04 GMT

Check out Invoke-Ternary here [link] Shay [link]

Powershell Refactored. – Introduction and Invoke Ternary.

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Powershell Refactored. – Introduction and Invoke Ternary. The purpose of this column is to present powershell