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All the Perl that's Practical to Extract and Report

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  • In my Mastering Perl class, I also show Memoize for the recursive solution, and bignum for all the solutions.

    So, are you working on this as an article for TPR? :)

  • How about

    sub fact
            my ( $n ) = @_;

            my @s = ();
            $s[0] = 1;

            foreach my $m ( 1 .. $n )
                    $s[$m] = 0;
                    for( my $k = $m;$k>=1;$k--)

  • Note that I am more interested in the algorithm than in the golfing or obsfuscation.

    I wouldn't call this golfing or obfuscation. It's another take on the classic recursive algorithm, and might not be interesting. Anyway, here's how I'd write the recursive version:

    sub factorial {
        my $v = shift;
        return 1 if $v == 1;
        return $v * factorial( $v - 1 );

    I like to get the terminating case out of the way early on, and then read the meat of the algorithm (or soy of the al

  • use List::Util qw(reduce);
    sub factorial {
        my $v = shift;
        return reduce { $a * $b } 1 .. $v;

    Too bad it produces spurious warnings:

    Name "main::a" used only once: possible typo at line 5.
    Name "main::b" used only once: possible typo at line 5.

  • sub factorial {
        my $f = 1;
        $f *= $_ for 2 .. shift;