Source code in the powershell programming language

function range-expansion($array) {
    function expansion($arr) { 
        if($arr) {
            $arr = $arr.Split(',')
             $arr | foreach{
                $a = $_
                $b, $c, $d, $e = $a.Split('-')
                switch($a) {
                    $b {return $a}
                    "-$c" {return $a}
                    "$b-$c" {return "$(([Int]$b)..([Int]$c))"}
                    "-$c-$d" {return "$(([Int]$("-$c"))..([Int]$d))"}
                    "-$c--$e" {return "$(([Int]$("-$c"))..([Int]$("-$e")))"}
                }
             }
        } else {""}
    }
    $OFS = ", "
    "$(expansion $array)"
    $OFS = " "
}
range-expansion "-6,-3--1,3-5,7-11,14,15,17-20"


function Expand-Range
{
    [CmdletBinding()]
    [OutputType([int])]
    Param
    (
        [Parameter(Mandatory=$true, 
                   Position=0)]
        [ValidateNotNullOrEmpty()]
        [ValidatePattern('^[0-9,-]*$')]
        [string]
        $Range
    )

    try
    {
        if ($Range -match '-,')       # I'm not good enough to weed this case out with Regex
        {
            throw "Input string was not in a correct format."
        }

        [int[]]$output = $Range -split ',' | ForEach-Object {

            [int[]]$array = $_ -split '(?<=\d)-'  

            if ($array.Count -gt 1)   # $array contains one or two elements
            {
                $array[0]..$array[1]  # two elements = start and end of range
            }
            else
            {
                $array                # one element = an integer
            }
        }
    }
    catch
    {
        throw "Input string was not in a correct format."
    }

    $output
}


(Expand-Range "-6,-3--1,3-5,7-11,14,15,17-20") -join ", "