Move elements in an array of hashtables to another array in PowerShell - arrays

Question

I'd like to move hashtables from one array to another.
Assuming that I have an array of hashtables:
PS> $a = #( #{s='a';e='b'}, #{s='b';e='c'}, #{s='b';e='d'} )
Name Value
---- -----
s a
e b
s b
e c
s b
e d
I can copy a selected set to another array:
PS> $b = $a | ? {$_.s -Eq 'b'}
Name Value
---- -----
s b
e c
s b
e d
Then remove b's items from a:
PS> $a = $a | ? {$b -NotContains $_}
Name Value
---- -----
s a
e b
Is there a more-succinct way of doing this?

Answer 1

PS 4.0 using Where method:
$b, $a = $a.Where({$_.s -Eq 'b'}, 'Split')
More info:
ForEach and Where magic methods

Answer 2

I would argue that doing two assignments with a filter and the inverted filter is the most straightforward way of doing this in PowerShell:
$b = $a | ? {$_.s -eq 'b'} # x == y
$a = $a | ? {$_.s -ne 'b'} # x != y, i.e. !(x == y)
You could wrap a function around this operation like this (using call by reference):
function Move-Elements {
Param(
[Parameter(Mandatory=$true)]
[ref][array]$Source,
[Parameter(Mandatory=$true)]
[AllowEmptyCollection()]
[ref][array]$Destination,
[Parameter(Mandatory=$true)]
[scriptblock]$Filter
)
$inverseFilter = [scriptblock]::Create("-not ($Filter)")
$Destination.Value = $Source.Value | Where-Object $Filter
$Source.Value = $Source.Value | Where-Object $inverseFilter
}
$b = #()
Move-Elements ([ref]$a) ([ref]$b) {$_.s -eq 'b'}
or like this (returning a list of arrays):
function Remove-Elements {
Param(
[Parameter(Mandatory=$true)]
[array]$Source,
[Parameter(Mandatory=$true)]
[scriptblock]$Filter
)
$inverseFilter = [scriptblock]::Create("-not ($Filter)")
$destination = $Source | Where-Object $Filter
$Source = $Source | Where-Object $inverseFilter
$Source, $destination
}
$a, $b = Remove-Elements $a {$_.s -eq 'b'}
or a combination of the above.