[PowerShell] A enumeration cmdlet of delayed evaluation.

Linq.ps1

function Where-Block
{
    [CmdletBinding()]
    [OutputType([scriptblock])]
    Param
    (
        [Parameter(Mandatory=$true,
                   ValueFromPipeline=$true,
                   Position=0)]
        [PSObject]
        $InputObject,
        [Parameter(Mandatory=$true,
                   Position=1)]
        [scriptblock]
        $Predicate
    )

    Begin
    {
    }
    Process
    {
        foreach($item in $InputObject)
        {
            return {
                if($item -is [scriptblock])
                {
                    $argument = &$item
                    if($argument -eq $null){ return }
                }else
                {
                    $argument = $item
                }

                [bool]$result = &$Predicate $argument
                if($result -eq $true)
                {
                    return $argument
                }
            }.GetNewClosure()
        }
    }
    End
    {
    }
}

function Select-Block
{
    [CmdletBinding()]
    [OutputType([scriptblock])]
    Param
    (
        [Parameter(Mandatory=$true,
                   ValueFromPipeline=$true,
                   Position=0)]
        [PSObject]
        $InputObject,
        [Parameter(Mandatory=$true,
                   Position=1)]
        [scriptblock]
        $Selector
    )

    Begin
    {
    }
    Process
    {
        foreach($item in $InputObject)
        {
            return {
                if($item -is [scriptblock])
                {
                    $argument = &$item
                    if($argument -eq $null){ return }
                }else
                {
                    $argument = $item
                }

                &$Selector $argument
                
            }.GetNewClosure()
        }
    }
    End
    {
    }
}

function Foreach-Block
{
    [CmdletBinding()]
    Param
    (
        [Parameter(Mandatory=$true,
                   ValueFromPipeline=$true,
                   Position=0)]
        [scriptblock[]]
        $Sequence,
        [Parameter(Position=1)]
        [scriptblock]
        $Action = $null
    )

    Begin
    {
    }
    Process
    {
        foreach($item in $Sequence)
        {
            $result = &$item
            if($result -eq $null) { continue }
            if($Action -eq $null)
            {
                $result
            }
            else
            {
                &$Action $result
            }
        }
    }
    End
    {
    }
}