<#
.SYNOPSIS
	Lists PI
.DESCRIPTION
        This PowerShell script calculates and lists the digits of the mathematical constant PI.
.PARAMETER digits
	Specifies the number of digits to list (10000 by default)
.EXAMPLE
        PS> ./list-pi
	3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342...
.LINK
        https://github.com/fleschutz/PowerShell
.NOTES
        Author: Markus Fleschutz | License: CC0
#>

param([int]$Digits = 10000)

function List-Pi ( $Digits ) {
	$Big = [bigint[]](0..10)
 
	$ndigits = 0
 
 	$q = $t = $k = $Big[1]
 	$r =           $Big[0]
	$l = $n =      $Big[3]

	# calculate first digit
	$nr = ( $Big[2] * $q + $r ) * $l
	$nn = ( $q * ( $Big[7] * $k + $Big[2] ) + $r * $l ) / ( $t * $l )
	$q *= $k
	$t *= $l
	$l += $Big[2]
	$k = $k + $Big[1]
	$n = $nn
	$r = $nr
 
 	Write-Host "$($n)." -noNewline
 	$ndigits++
 
 	$nr = $Big[10] * ( $r - $n * $t )
 	$n = ( ( $Big[10] * ( 3 * $q + $r ) ) / $t ) - 10 * $n
 	$q *= $Big[10]
 	$r = $nr
 
 	while ($ndigits -lt $Digits) {
		if ($Big[4] * $q + $r - $t -lt $n * $t) {
			Write-Host "$n" -noNewline
			$ndigits++
			$nr = $Big[10] * ( $r - $n * $t )
			$n = ( ( $Big[10] * ( 3 * $q + $r ) ) / $t ) - 10 * $n
			$q *= $Big[10]
			$r = $nr
		} else {
			$nr = ( $Big[2] * $q + $r ) * $l
			$nn = ( $q * ( $Big[7] * $k + $Big[2] ) + $r * $l ) / ( $t * $l )
			$q *= $k
			$t *= $l
			$l += $Big[2]
			$k = $k + $Big[1]
			$n = $nn
			$r = $nr
		}
        }
}

try {
	List-Pi $Digits
	exit 0 # success
} catch {
        "⚠️ Error in line $($_.InvocationInfo.ScriptLineNumber): $($Error[0])"
        exit 1
}