Day 15 – Building a (little) Spacecraft with Perl 6

Showing off long ears

In the previous post, we have encountered some kind of special elves’ magic:

enum Fuel <Solid Liquid Gas>;

class SpeedChoice does ASNChoice {
    method ASN-choice { { mph => (1 => Int), kmph => (0 => Int) } }

class Rocket does ASNSequence {
    has Str $.name is UTF8String;
    has Str $.message is default-value("Hello World") is UTF8String;
    has Fuel $.fuel;
    has SpeedChoice $.speed is optional;
    has Str @.payload is UTF8String;

    method ASN-order { <$!name $!message $!fuel $!speed @!payload> }

my $rocket =
    name => 'Falcon',
    fuel => Solid,
    speed => => 18000)),
    payload => [ "Car", "GPS" ]);

my $rocket-bytes = ASN::Serializer.serialize($rocket, :mode(Implicit));

#`[ Result:
          0x30, 0x1B, # Outermost SEQUENCE
          0x0C, 0x06, 0x46, 0x61, 0x6C, 0x63, 0x6F, 0x6E, # NAME, MESSAGE is missing
          0x0A, 0x01, 0x00, # ENUMERATED
          0x81, 0x02, 0x46, 0x50, # CHOICE
          0x30, 0x0A, # SEQUENCE OF UTF8String
              0x0C, 0x03, 0x43, 0x61, 0x72,  # UTF8String
              0x0C, 0x03, 0x47, 0x50, 0x53); # UTF8String

say$rocket-bytes) eqv $rocket; # Certainly true!

However, as an elf I know once quoted, ‘It’s hard to tell the difference between mastered technique and magic’. So the mystery can be resolved? Let’s glance over the way it all works.

Continue reading “Day 15 – Building a (little) Spacecraft with Perl 6”

Day 14 – Designing a (little) Spacecraft with Perl 6

Looking for a common point


Those days I am spending some of my time working on foundation parts for, revealing a possible surprise, a LDAP (Lightweight Directory Access Protocol) implementation for Perl 6.

However, it is yet too early to talk about this one, so I will have some mystery blanket covering this topic for now, as we have another one – spacecrafts!

And a common point between spacecrafts and LDAP is: LDAP specification uses a notation called ASN.1, which allows one to define an abstract type, using a specific textual syntax, and, with a help of ASN.1 compilers, create a type definition for particular programming language and what’s more: encoder and decoder for values of this type, which can serialize your value into some data which, for example, can be send over network and parsed nicely on another computer.

Continue reading “Day 14 – Designing a (little) Spacecraft with Perl 6”

Day 13 – Web server from scratch with Cro and Debian

I talked to Santa Claus and he said he does not know how to install Cro on Debian, so I said to myself: I’m going to help him out.

If you have some experience with web servers like Apache, and you have heard about the powerful concurrent/reactive aspects of Perl6, surely you are interested to know about Cro Services. The scope of this post are people with basic experience in Debian and basic experience or none in Perl6… like Santa.

Cro is a Perl6 module that gives everything you need to build reactive and concurrent services easily, for example: a web server.

In this post we will see how to install Cro from scratch in Debian, one of the most popular Linux distributions. Then, I will explain the demo example of Cro.

We will use Debian 9, 64-bit (Stretch) and we will start once it is installed.

Continue reading “Day 13 – Web server from scratch with Cro and Debian”

Day 12 – Building a flexible grammar

Mrs Santa has written a basic grammar to match the simple lists that GDPR ignorant elves are collecting from around the world about who has been naughty or nice this year.

Each record is a name, followed by a tab, followed by an address, followed by a tab, followed by an assessment of naughty or nice and then finishes with a newline.

Batman 1 Batman Street, Gotham Nice
Joker 5 Joker Street, Arkham Naughty
Riddler 12 Riddler Street, Arkham Naughty
Robin 2 Robin Street, Gotham Nice

She wants to filter off the Naughty people into one list and the Nice people into another, as Krampus is going to deal with all the naughty people this year. Continue reading “Day 12 – Building a flexible grammar”

Day 11 – Testing your Times Tables with Perl 6

It’s nearly the end of Winter term at Elf Primary School near the North Pole. A keen head for figures is very important to elves, and the little elves’ numeracy teacher, Ms Hopper, wants to make sure they keep up their arithmetical skills right up to the penultimate day of term. (The last day of term is reserved for watching films and playing shove-ha’penny).

The little elves have just learned their times tables (multiplication tables) up to 12, but they aren’t all as good at it as they’d like to be, and some of them will be helping out in the toy workshops just before Christmas, when they may need to quickly tell the big elves how many more toys of a particular type to make.

Fortunately Elf Hopper is a very smart elf with an excellent head for figures – and code – herself. So she whips up a quick console app to run on the little elves’ school-issue Perlix 6.0 boxen.

The program allows the little elves to test themselves on their 2 to 12 times tables by just running it, or if they supply a single numeric argument, they can try out any multiplication table they like.

Continue reading “Day 11 – Testing your Times Tables with Perl 6”

Day 10 – jmp-starting your work flow

Here’s yet another version of jmp for you to unwrap before Christmas.

jmp is a command-line tool for searching through piles of code and then quickly jumping into an $EDITOR. This helps to keep things flowing.

Computer programming, however, has plenty of potential flow stoppers. To maintain a state of flow while coding you often need to quickly jmp to a line of code in other situations: fixing bugs, running tests, inspecting log files, checking git status etc. Can jmp help speed up these tasks too?

Continue reading “Day 10 – jmp-starting your work flow”

Day 9 – Let’s get astroPhysical! – Constants in Perl 6

I wrote my first Perl 6 program (that is, one that worked) the day before the London Perl Workshop where I proudly told people. So, JJ says “Why don’t you write an Advent calendar post for Perl 6?”

With only one program under my belt, what do I have to write about? Well … I authored Astro::Constants in Perl 5, so how hard would it be to migrate it to Perl 6?

Since I couldn’t keep my big gob shut, I give you the tale of a Perl 5 module author wandering through the Perl 6 landscape.

Continue reading “Day 9 – Let’s get astroPhysical! – Constants in Perl 6”

Day 8 — Make your Perl 6 grammar compact

Welcome to Day 8 of this year’s Perl 6 Advent Calendar!

Grammars are among many things that make Perl 6 a great programming language. I would not even try predicting the result of a poll to choose between grammars, Unicode support, concurrency features, hyper-operators, or the set syntax, or a Whatever star. Google found its own list of the best Perl 6 features published on the Internet.

Anyway, today we’ll be talking about Perl 6 grammars, and I will share a few tricks that I use to make the grammars more compact.

Continue reading “Day 8 — Make your Perl 6 grammar compact”

Day 7 – Automatic on a Cellular Level

Today’s advent calendar post deals with Cellular Automata.

What are cellular automata? I’m glad you asked! They are systems made up of only a few parts: A kind of field or “world” made up of cells, a set of states that every cell can be in at any point, a “neighborhood” describing what cells are visible to each cell, and a set of rules governing what a cell will change its state into given its own state and the state of all cells in its neighborhood.

That is, of course, a very abstract description, so let me give a few examples for the individual parts to hopefully give you an idea of what you might see in a cellular automaton:

In typical worlds you might find cells arranged like beads on a string, or like fields on a chess or chinese checkers board. There are also more exotic configurations you can make up: Any 2-dimensional field can be mapped onto any surface, like for example the Stanford bunny.

Continue reading “Day 7 – Automatic on a Cellular Level”