#!/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;
        }
}

##</code><code>##

Benchmark: timing 1000000 iterations of Closure, Global, Lexical, Recursion...
   Closure: 66 wallclock secs (61.70 usr +  0.00 sys = 61.70 CPU) @ 16207.46/s (n=1000000)
    Global: 62 wallclock secs (58.39 usr +  0.00 sys = 58.39 CPU) @ 17126.22/s (n=1000000)
   Lexical: 63 wallclock secs (58.55 usr +  0.00 sys = 58.55 CPU) @ 17079.42/s (n=1000000)
 Recursion: 208 wallclock secs (176.95 usr +  0.00 sys = 176.95 CPU) @ 5651.31/s (n=1000000)