PowerShell as LINQ

PowerShellAsLinq.ps1

# ----------------------------------------------------------------------------------------------------------
# PowerShell as LINQ
#  * When I created this snippet, the blog written by NyaRuRu-san was very helpful.
#    I would like to thank him for his article: 
#    - PowerShell で LINQ - NyaRuRuの日記: http://d.hatena.ne.jp/NyaRuRu/20080112/p2 
#
# Change History
#  * 2012/06/20 07:23:24: Fix the bug that occurs unintended pipeline breaking.
#                         The keyword 'return' is reserved, so I use the function name 'run' instead of it.
#  * 2012/06/23 22:26:47: Fix the bug that function 'run' doesn't stop enumeration.
#                         Add function 'flatten' that makes the list flat.
#                         Add function 'first'. It is shortcut equivalent to 'take 1'.
# ----------------------------------------------------------------------------------------------------------

function __extract__([Collections.IEnumerator]$enum)
{
    foreach ($val in $enum)
    {
        $block = $val -as [scriptblock]
        if ($block -eq $null)
        {
            throw New-Object ArgumentException('The pipeline source object must be a scriptblock.')
        }
        break
    }
    $block    
}

function repeat([scriptblock]$init)
{
    {
        $elem = &$init 
        try
        {
            while ($true) 
            { 
                ,$elem 
            } 
        }
        finally
        {
            $disp = $elem -as [IDisposable]
            if ($disp -ne $null)
            {
                $disp.Dispose()
            }
        }
    }.GetNewClosure()
}

function take([int]$count)
{
    $block = __extract__ $input
    {
        $count = $count 
        &$block | 
        %{ 
            if ($i++ -ge $count)
            {
                break
            }
            ,$_
        }.GetNewClosure()
    }.GetNewClosure()
}

function map([scriptblock]$func)
{
    $block = __extract__ $input
    {
        $func = $func 
        &$block | 
        %{
            ,(&$func $_)
        }.GetNewClosure()
    }.GetNewClosure()
}

function flatten([scriptblock]$func)
{
    $block = __extract__ $input
    {
        $func = $func 
        &$block | 
        %{
            &$func $_ | %{,$_}
        }.GetNewClosure()
    }.GetNewClosure()
}

function filter([scriptblock]$func)
{
    $block = __extract__ $input
    {
        $func = $func 
        &$block | 
        %{
            if (&$func $_)
            {
                ,$_
            }
        }.GetNewClosure()
    }.GetNewClosure()
}

function takeWhile([scriptblock]$func)
{
    $block = __extract__ $input
    {
        $func = $func 
        &$block | 
        %{
            if (&$func $_)
            {
                ,$_
            }
            else
            {
                break
            }
        }.GetNewClosure()
    }.GetNewClosure()
}

function first
{
    __extract__ $input | take 1
}

function run
{
    do 
    {
        &(__extract__ $input)
    } until ($true)
}



# ----------------------------------------------------------------------------------------------------------
# Usage
# ----------------------------------------------------------------------------------------------------------

# dump win.ini
repeat {New-Object IO.StreamReader 'C:\Windows\win.ini'} |
    map {param($_1) $_1.ReadLine()} |
    takeWhile {param($_1) $_1 -ne $null} |
    run

# the sample results are as follows: 
#
# ; for 16-bit app support
# [fonts]
# [extensions]
# [mci extensions]
# [files]
# [Mail]
# MAPI=1
# CMCDLLNAME32=mapi32.dll
# CMC=1
# MAPIX=1
# MAPIXVER=1.0.0.1
# OLEMessaging=1
# [MCI Extensions.BAK]
# 3g2=MPEGVideo
# 3gp=MPEGVideo
# 3gp2=MPEGVideo
# 3gpp=MPEGVideo
# aac=MPEGVideo
# adt=MPEGVideo
# adts=MPEGVideo
# m2t=MPEGVideo
# m2ts=MPEGVideo
# m2v=MPEGVideo
# m4a=MPEGVideo
# m4v=MPEGVideo
# mod=MPEGVideo
# mov=MPEGVideo
# mp4=MPEGVideo
# mp4v=MPEGVideo
# mts=MPEGVideo
# ts=MPEGVideo
# tts=MPEGVideo



# get 5 random numbers of one digit.
repeat {New-Object Random} |
    map {param($_1) $_1.Next(0, 10)} |
    take 5 |
    run

# the sample results are as follows: 
#
# 4
# 8
# 6
# 8
# 5



# countdown for 10 seconds
$last = 0
repeat {(Get-Date).AddSeconds(10.0)} |
    map {param($_1) $_1 - (Get-Date)} |
    takeWhile {param($_1) $_1.TotalSeconds -gt 0} |
    run |
    %{if ($last -ne $_.Seconds){$last = $_.Seconds; $_.Seconds}}

# the sample results are as follows(NOTE: each object will be displayed every second): 
#
# 9
# 8
# 7
# 6
# 5
# 4
# 3
# 2
# 1
# 0



# enumerate each first type in each assembly from current AppDomain
{[AppDomain]::CurrentDomain.GetAssemblies()} | 
    flatten {param($asm) {$asm.GetTypes()} | 
                              first | 
                              map {param($t) $t.AssemblyQualifiedName} | 
                              run} | 
    run

# the sample results are as follows: 
#
# System.Object, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
# AssemblyStrings, Microsoft.PowerShell.ConsoleHost, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
# FXAssembly, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
# System.Management.Automation.ChildItemCmdletProviderIntrinsics, System.Management.Automation, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
# Microsoft.PowerShell.Commands.GetWinEventCommand, Microsoft.PowerShell.Commands.Diagnostics, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
# Microsoft.Contracts.PureAttribute, System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
# FXAssembly, System.Configuration.Install, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
# Microsoft.WSMan.Management.WSManConfigProvider, Microsoft.WSMan.Management, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
# System.Transactions.SRDescriptionAttribute, System.Transactions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
# Microsoft.PowerShell.Commands.Internal.Format.FrontEndCommandBase, Microsoft.PowerShell.Commands.Utility, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
# Microsoft.PowerShell.Commands.CoreCommandBase, Microsoft.PowerShell.Commands.Management, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
# Microsoft.PowerShell.Commands.SecurityDescriptorCommandsBase, Microsoft.PowerShell.Security, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
# FXAssembly, System.Xml, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
# System.Management.SRDescriptionAttribute, System.Management, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
# FXAssembly, System.DirectoryServices, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
# SNINativeMethodWrapper, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
# FXAssembly, System.Configuration, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
# System.Security.SecurityResources, System.Security, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
# System.Xml.Utils.ResDescriptionAttribute, System.Data.SqlXml, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089