#!/usr/bin/perl -w
use strict;
use Benchmark qw/:all/;
my $iGlobal;

my $x = 4;

timethese (1000000,
{
'Recursion' => 'Rfactorial(30)',
'Global' => 'Gfactorial(30)',
'Lexical' => 'Lfactorial(30)',
'Closure' => '&{Cfactorial()}(30)',
}
);

# A classic, recursive soulution.
sub Rfactorial {
        my $i = shift;
        return 1 if $i == 0;
        return 1 if $i == 1;
        return $i * Rfactorial($i - 1);
}

# Rewritten to use global variables.
sub Gfactorial {
        $iGlobal = shift;

        return 1 unless $iGlobal > 1;
        my $result = 1;
        while ($iGlobal > 1) {
                $result = $result * $iGlobal;
                $iGlobal--;
        }
        return $result;
}

# expressed with lexicals
sub Lfactorial {
        my $iLexical = shift;

        return 1 unless $iLexical > 1;
        my $result = 1;
        while ($iLexical > 1) {
                $result = $result * $iLexical;
                $iLexical--;
        }
        return $result;
}


# Rewritten to use closures

sub Cfactorial {
        my $iClosure;
        return sub {
                my $iClosure = shift;
                my $result = 1;
                while ($iClosure > 1) {
                        $result = $result * $iClosure;
                        $iClosure --;
                }
                return $result;
        }
}