Rakudo ng - what will it mean for us?

If you've been hanging around the right blogs and the #perl6 IRC channel on Freenode, then you've probably seen references to a slightly mysterious "ng", or "Rakudo ng".

That's the upcoming (next) version (generation) of Rakudo, which will form the basis for Rakudo *.

In essence, this is a refactoring/rewrite of Rakudo for the purpose of better compliance with the specification and performance improvements (yay). The old Rakudo master made it difficult — if not impossible — to implement several essential parts of the Perl 6 spec and top priorities on the Rakudo roadmap.

In January, this has led to less focus on the current Rakudo version's bugs and gotchas, and instead on working to prepare ng as the new master branch — that is, the Rakudo that you will be downloading the next time.

For those of us who do some Perl 6 coding in Rakudo, this means that we can expect a nice little bunch of incompatibilities as compared to the current master. And yes, it's very close, so it's time to prepare.

Here's a list of the blindingly obvious things I think we need to watch out for:

• Older Rakudo was not in line with parts of the spec that ng will be.
• The spec has changed. (ng development has uncovered several necessary changes.)
• Older Rakudo is in line with parts of the spec that ng perhaps isn't.
• Rakudo ng is, of course, not feature complete when it replaces older Rakudo as the master.

In other words: let's not fool ourselves into thinking that we all of a sudden have a new Rakudo that's both compatible with the older as well as being spec compliant.

The good news about Rakudo ng

If you judge by the above paragraphs, you'd think that Rakudo ng was bad for Perl 6 developers. But that's far off the mark. I prodded #perl6 and Patrick Michaud before publishing this post, and here's a brief summary of (most of) the improvements we can see coming with Rakudo ng as opposed to the current implementation.

• Most of the top priorities of the Rakudo roadmap will be implemented!
• Laziness will mostly work (the spec is undergoing change)
• Performance improvements, many due to laziness
• Array/List/Parcel/etc. will be compliant with the updated spec
• Protoregexes
• Better longest token matching
• Meta-operators are really meta, and generated on demand
• The base object metamodel is far closer to the spec than before
• Major portions of the metamodel are implemented in Perl 6
• Array and hash vivification will work properly
• Lexical subs and variables work properly
• Operators have the correct names (with angles)
• Subs have the correct sigils (with ampersands)
• Phasers work, and the phaser model is much improved

Our programs will need a bit of attention. I recommend subscribing to perl6-language for up-to-date information about changes to the specification and language discussions.

There's still a lot of work to be done, and I'm sure the Perl 6 developers are happy for any help they can get.

Dice Rolls for Role-Players

I realize that the title of this post is a bit of an oxymoron, because a Real Role-Player of course doesn't roll dice often. ;)

But in the cases where the Real Role-Player does roll dice, wouldn't it be nice to have a computer program to forget at home rather than some even more easily mislaid dice?

The Perl 6 Advent Calendar provided some inspiration for this post.

A problem with many minor programming examples you see on the net, is that they do not take into account the needs of a role-player. Role-players play many different systems, with different criteria for success in dice rolls. D6 (the regular six-sided cubic dice used for playing Monopoly, Yahtzee, etc.) are not used much in the majority of systems.

Therefore, I'll look at the Storyteller System, which is used in the World of Darkness series of games.

The general principle is that you have a pool of dice to roll, and you count your successes, which in this system is the number of dice that have a value greater than or equal to a given target number for the roll. The standard target number is 8 in most implementations. Five successes in the same roll is an exceptional success. Obviously, it's nice to have many dice to roll!

Here's a real Perl 6 program that works with Rakudo today: it accepts two command line parameters, the first being the size of the dice pool, the optional second parameter defines the target number for success:

---

use v6;

subset D10 of Int where 1..10;

sub is_success (D10 $roll, D10 $target) {
    my $n = 0;
    if ($roll == 10) {
        say "10 again";
        $n += roll 1,$target;
    }
    $roll >= $target ?? $n + 1 !! $n;
}

sub roll (Int $poolsize where { $_ > 0 }, D10 $target? = 8) {
    my D10 @rolls = (1..10).pick($poolsize, :replace);
    say "Roll: " ~ @rolls.sort.join(",");
    [+] @rolls.map: { is_success $_,$target };
}

given @*ARGS.elems {
    when 2   {
               say "Target number: " ~ @*ARGS[1];
               continue;
             }
    when 1|2 {
               my $n = roll |@*ARGS>>.Int;
               say "Successes rolled: " ~ $n;
               $n >= 5 and say "Exceptional success!";
             }
    when *   {
               $*ERR.say("roll.p6 poolsize [target]");
               exit(64);
             }
}

---

Thanks to moritz++ for ironing out two annoying mistakes!

Here are a few usage examples:

---

$ perl6 roll.p6
roll.pl poolsize [target]

$ perl6 roll.p6 5
Roll: 1,2,7,8,9
Successes rolled: 2

$ perl6 roll.p6 5 2
Target number: 2
Roll: 1,2,2,4,9
Successes rolled: 4

$ perl6 roll.p6 5 4
Target number: 4
Roll: 6,8,9,10,10
10 again
Roll: 8
10 again
Roll: 2
Successes rolled: 6 - Exceptional success!

---

There are no comments in this piece of code, I want people to try to understand it as-is, based on the Perl 6 Advent Calendar. If you have any questions, comments, corrections, etc., don't hesitate, just write!

In my next blog entry, I'll pick the program apart and comment on what I've done and why, and who knows, maybe someone has come up with an elegant solution to the same problem.

What stops me from using Perl 6, today?

Since I got hooked on the Perl community, and got a taste of Perl 6, I've been wondering about:

1. what, exactly, is it that I could use Perl 6 for, right now?
2. why am I not actively using Perl 6 now?

Those are easy questions, but answering is hard, so this may be a long post.

Sure, the points listed below are not exactly Perl 6 specific; I could probably have picked some other programming language, but I somehow feel more comfortable in the way that Perl 6 still is Perl.

What I could use Perl 6 for right now

I think it's fair to say that using Perl 6 today mostly means using Rakudo, and that I wouldn't use it in what we popularly call a "production setting". But many of us programmers, sysadmins, geeks and nerds have perfectly suitable hobby projects, where we won't have clients wringing our necks if there is three minutes of downtime in a month, or if we don't deliver the Speedy Gonzalez of services; we have projects that are neither computing performance constrained or stability constrained.

So that's where I could have started using Perl 6 half a year ago, and of course still can.

I know I can use Perl 6 for e.g. a fairly complex web site using Web.pm and Squerl for a SQLite backend. It will probably work just fine, for a lot of projects.

I know I can use it for lots of one-liner scripts.

I know that in some regards, Perl 6 will outperform classic Perl 5 in terms of programmer time spent. An example is the given-when control structure, which (to me) is semantically superior to if-elsif-elsif-elsif. Programmer time is important to me, I hate coding too much for menial tasks. And I'm sorry to say that Perl 5.10 doesn't do it yet for me, as I cannot rely on its presence, even for hobby projects.

And I know I can use Perl 6 to refresh some of the knowledge about programming language specifics (terminology, technique, methodology, etc.) that I've allowed to rust since I left university in 2001.

Concrete projects, in no particular order

• web page for registration of pool billiards tournament results; it's not performance critical, and the users could check and verify the dataset themselves after input


• conversion of historical results data in CSV format to a database; one-time job, needs manual verification no matter what programming language I use to do it


• contributing to the Temporal.pm specification and implementation in Perl 6


• personal web gallery generation; I positively loathe most of the online galleries, because they sooner rather than later are discovered to have HUGE, GAPING security vulnerabilities


• blogging tool; I'm not very comfortable with blog software running on servers, either, and whatever blogging I do, it's not actual work

That's quite a lot, isn't it? It ought to have been enough to get me going in a jiffy!

Why I'm not actively using Perl 6 now

This may be a surprise to some: it's not because of a lack of matureness in the tools, a lack of confidence in the language or tools, stability issues, etc. As I tangentially mentioned above, I believe there is no technical hindrance for me to start coding on a hobby project.

I have plenty of hobby projects to choose from. They are also quite manageable in terms of eventual lines of code.

However, there is something holding me back, and that's a certain degree of perfectionism mixed with procrastination fever.

mst mentioned during the NPW hackathon this spring that perfectionism was a barrier against getting started. If you're too obsessed with getting things right at first, at wanting to avoid failure, procrastinating is too easy. Getting slightly intoxicated (yup, drinking alcohol, which of course is only a recourse for adults) is a way of reducing your own perfection anxiety. This is almost exactly what Randall Munroe's xkcd calls the Ballmer Peak:



But I don't sleep too well after drinking alcohol, and I also tend to do hobby projects in my "running breaks" during work hours, in which case alcohol intake may be a very bad idea.

In addition, my time at work is a series of interruptions, which really isn't conductive to sitting down and learning something new and complex.

When I get home from work, I'm usually so fed up with computers that I don't want to have anything to do with them.

So my spare time, whatever is left of it, usually isn't spent on programming. Note that I don't even do these projects in a programming language I already know well; they are on hold regardless of that.

All in all, there's nothing much wrong with Perl 6.

Blaming the immaturity of Rakudo would just be a silly excuse. There's something wrong with my capacity for finding the time to get down and dirty with it, that's what; I'm apparently not currently capable of saying honestly:

This is my Perl 6 hour. This hour, I'm going to do Perl 6 stuff, and this time is sacred.