Functions/Get-Factorial.ps1
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function Get-Factorial { <# .SYNOPSIS Determine the factorial of a given integer value .DESCRIPTION Recursive function to determine the factorial of a given integer value. Values must be in range of 0-20 .PARAMETER Value Array of integers each of which should be in the range of 0-20. Accepts values from the pipeline .PARAMETER IncludeInput Switch to include the input parameter into the output .EXAMPLE Get-Factorial -Value 5 120 .EXAMPLE Get-Factorial -Value (1..5) -IncludeInput Value Factorial ----- --------- 1 1 2 2 3 6 4 24 5 120 .EXAMPLE 1..5 | Get-Factorial -IncludeInput Value Factorial ----- --------- 1 1 2 2 3 6 4 24 5 120 .EXAMPLE Get-Factorial -Value 3 -Verbose VERBOSE: Starting [Get-Factorial] VERBOSE: CurValue is [3] VERBOSE: Starting [Get-Factorial] VERBOSE: CurValue is [2] VERBOSE: Starting [Get-Factorial] VERBOSE: CurValue is [1] VERBOSE: Ending [Get-Factorial] VERBOSE: Ending [Get-Factorial] 6 VERBOSE: Ending [Get-Factorial] .EXAMPLE Get-Factorial -Value -1 Get-Factorial : CurValue [-1] must be between 0 and 20 At line:1 char:1 + Get-Factorial -Value -1 + ~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorException + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Get-Factorial #> [cmdletbinding()] param( [Parameter(Mandatory, ValueFromPipeline)] [int[]] $Value, [switch] $IncludeInput ) begin { Write-Verbose -Message "Starting [$($MyInvocation.Mycommand)]" } process { foreach ($CurValue in $Value) { Write-Verbose -Message "CurValue is [$CurValue]" if (($CurValue -lt 0) -or ($CurValue -gt 20)) { Write-Error -Message "CurValue [$CurValue] must be between 0 and 20" } else { if ($CurValue -eq 0) { [int64] $Result = 0 } elseif ($CurValue -eq 1) { [int64] $Result = 1 } else { [int64] $Result = $CurValue * (Get-Factorial -Value ($CurValue - 1)) } if ($IncludeInput) { New-Object -TypeName psobject -Property ([ordered] @{ Value = $CurValue Factorial = $Result }) } else { Write-Output $Result } } } } end { Write-Verbose -Message "Ending [$($MyInvocation.Mycommand)]" } } |