Reverse elements via pipeline

You can cast $input within the function directly to a array, and then reverse that:

function reverse { $arr = @($input) [array]::reverse($arr) $arr } 

10, 20, 30 | Sort-Object -Descending {(++$script:i)} 

Here's a remarkably compact solution:

function Reverse { [System.Collections.Stack]::new(@($input)) } 

One-liners inspired by this answer:

10,20,30 -as 'Collections.Stack' | Write-Verbose -vb 

[Collections.Stack](10,20,30) | Write-Verbose -vb 

10,20,30 | &{ @($Input) -as 'Collections.Stack' } | Write-Verbose -vb 

10,20,30 | &{ [Collections.Stack]@($Input) } | Write-Verbose -vb 

The first one looks the nicest, the second one is the shortest, and the last two are for performing the reversal mid-pipeline rather than before the pipeline.

$array = 10,20,30; (($array.Length - 1)..0) | %{ $array[$_] } 

Here's one approach:

function Reverse () { $arr = $input | ForEach-Object { $_ } [array]::Reverse($arr) return $arr } 

Using $input works for pipe, but not for parameter. Try this:

function Get-ReverseArray { Param( [Parameter(Mandatory = $true, Position = 0, ValueFromPipeLine = $true)] $Array ) begin{ $build = @() } process{ $build += @($Array) } end{ [array]::reverse($build) $build } } #set alias to use non-standard verb, not required.. just looks nicer New-Alias -Name Reverse-Array -Value Get-ReverseArray 

Test:

$a = "quick","brown","fox" #--- these all work $a | Reverse-Array Reverse-Array -Array $a Reverse-Array $a #--- Output for each fox brown quick 

I realize this doesn't use a pipe, but I found this easier if you just wanted to do this inline, there is a simple way. Just put your values into an array and call the existing Reverse function like this:

$list = 30,20,10 [array]::Reverse($list) # print the output. $list 

Put that in a PowerShell ISE window and run it the output will be 10, 20, 30.

Again, this is if you just want to do it inline. There is a function that will work for you.

You can use Linq.Enumerable.Reverse. Either of the following work:

,(10, 20, 30) | % { [Linq.Enumerable]::Reverse([int[]]$_) } ,([int[]]10, 20, 30) | % { [Linq.Enumerable]::Reverse($_) } 

The two challenges are putting the whole array into the pipeline rather than one element at a time (solved by making it an array of arrays with the initial comma) and hitting the type signature of Reverse (solved by the [int[]]).

10, 20, 30 | Sort-Object @{e={(++$script:i)};d=$true} 

same in full syntax:

10, 20, 30 | Sort-Object -Property @{Expression={(++$script:i)}; Descending=$true} 

$i shouldn't be local, so I use script scope modifier

() inside {} are needed to return the value of the calculation

Thus, each element acquires a "virtual property" with a serial number. By which it is sorted in reverse order.