While replying to 340465, I started playing with various implementations of a recursive factorial generator, trying to see which was fastest. I came up with: 
{
    my ($end, $result, $_fact);
    $_fact = sub { $end ? ($result *= $end-- and &$_fact) : $result }
    sub fact { ($end, $result) = (shift, 1); &$_fact }
}

[download]

I'm curious about a few things:

  1. Can anyone beat that with a recursive implementation?
  2. What is the fastest factorial implementation?
  3. What other similar problems can we work through with this?
  4. Is there a CPAN-able module somewhere in this? Common::Functions?

If this generates more than one category, I'll put the top-3 from each category on my home-node.

Update: Benchmarks are good things. Please support anything you say with actual trials.

Update2: I didn't mean to start a discussion of factorial algorithms. I was curious as to see what micro-optimizations other monks know to uselessly speed up algorithms. Other options beside factorial would be fibonacci, md5, sha1, and other calculating algorithms.

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Then there are Damian modules.... *sigh* ... that's not about being less-lazy -- that's about being on some really good drugs -- you know, there is no spoon. - flyingmoose

In reply to What is the fastest pure-Perl implementation of XXX? by dragonchild

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