Perl 6 Introduction
perl6intro.com
perl6intro.com
So far I've gotten the impression it's made by a bunch of smart, friendly hackers who care about quality in their software.
To anyone reading this, I'd strongly recommend casting aside any preconceived notions about perl and giving perl6 an honest shot.
- optional, well-integrated gradual typing system.
- perl6 is the first mainstream(ish) dynamic language to not suffer from a GIL of some kind. You can do real concurrency and parallelism in perl6.
- perl6 is both equally as powerful, and much more simple than previous versions of perl.
- a bunch of good ideas stolen from other languages. go-routines are in there, pattern-matching, gradual typing, classes, etc. Plus, functional programming is a first-class-citizen of perl6. There's so much good stuff in there.
- overall, I think perl6 has the potential to become a very powerful (and yet robust and well engineered) hacker language, where you will not be constrained by implementation details of the VM the language runs on (I'm looking at you, GIL).
I'd also recommend reading Curtis Poe's answer to a similar question:
https://www.quora.com/Perl-programming-language-1/Should-I-b...
I went digging to try and understand what this meant, and seems it's referring to syntactic support for promises, which in at least the Rakudo implementation amount to a wrapper around a forking multiprocessing system (like the Python multiprocessing module).
From my perspective this concurrency isn't any more "real" than equivalents available in existing languages, but maybe I'm looking at the wrong thing - you mention global interpreter locks, and usually they refer to threading.
Does some implementation of perl6 have non-GIL threading?
edit: from <https://perl6advent.wordpress.com/2012/12/11/day-11-parrot-t...:
> The solution for these problems implemented in hybrid threads is to sidestep them altogether by disallowing write access to shared variables. The programmer (or in most cases the compiler) is obliged to declare a list of all shared variables before a newly created task is started. The interpreter would then create proxy objects for these variables which the task can use to access the data. These proxies contain references to the original objects. They use these references to forward all reading vtable functions to the originals. Write access on the other hand would lead to a runtime error.
> In other words, all data is owned by the thread creating it and only the owner may write to it. Other threads have only read access.
> For threads to be able to communicate with their creators and other threads, they still need to write to shared variables. This is where green threads come into play. Since green threads are light weight, it is feasible for a thread to create a task just for updating a variable. This task is scheduled on the interpreter owning this variable. To reduce latency, the task is flagged to run immediately. The data-owning interpreter will preempt the currently running task and process the new write task. Put another way, the data-owning interpreter is told what to write to its variables, so other threads don’t have to.
It's pretty clear the GP knows what a GIL is, he's wondering if Perl 6 is truly GIL-free, or if it "just" abstracts out the GIL using language primitives for a forking multiprocess system (already, that's a nice step, but it's not "GIL-free").
I'd like to know the same thing.
Rakudo's had more testing since it's been around forever but MoarVM is where my hopes lie. Here's hoping user adoption isn't fractured that badly like D's Tango vs Phobos debacle (which only now it's recovering from, I'd argue largely due to Andrei Alexandrescu's charismatic persona, haha.) Perl 6 is a really interesting language and I'd encourage you all to play with it, but it's an entirely different beast than Perl 5. They should have just renamed it entirely.
Is that wrong? If not, did you mean "Rakudo on Parrot" or "Rakudo on the JVM" when you wrote just "Rakudo"?
It's like this: Rakudo -> NQP -> MoarVM
or like this: Rakudo -> NQP -> NQP-JVM implementation -> JVM
Want to get Perl 6 running on the .Net CLR? Implement an NQP interpreter (which is supposed to be fairly easy) and you're 99% done (at least that's my understanding).
Sure, MoarVM is by design semantically close to NQP, but if you look at
$ nqp-m --stagestats -e ''
Stage start : 0.000
Stage parse : 0.003
Stage ast : 0.000
Stage optimize : 0.000
Stage mast : 0.005
Stage mbc : 0.000
Stage moar : 0.000
$ nqp-j --stagestats -e ''
Stage start : 0.000
Stage classname : 0.045
Stage parse : 0.067
Stage ast : 0.000
Stage optimize : 0.009
Stage jast : 0.145
Stage classfile : 0.010
Stage jar : 0.000
Stage jvm : 0.003
The current VMs are MoarVM, JVM, and some are working on a JavaScript backend.
Parrot isn't wholly abandoned, but Reini Urban is the only person still hacking on it. On the other hand, he is the person most likely to bring Parrot back around to being a good backend for Perl 6, so it has that going for it.
Currently no implementation of Perl 6 targets Parrot. Rakudo used to (indeed, was born on Parrot), but suspended support for Parrot in connection with the push to get Rakudo-on-MoarVM up to 6.0.0 quality by Christmas. The Rakudo team were careful not to say they were writing Parrot off, but they also gave no particular criteria for when they would unsuspend it.
(I in no way speak for Rakudo or anyone else, but I suspect the implicit criteria for unsuspension are three: Parrot must demonstrate, in code, that being a good backend for Perl 6 is a higher priority than being a good backend for entirely hypothetical other clients; it must undertake, survive, and complete a major decrufting if not re-architecting; and of course, it must be more interesting, for enough people, to target Parrot than to hack Perl 6 on Moar, JVM, JS, Mono, the perl5 VM, p2, WebAssembly, native code, the Factor VM, or whatever else.)
There are also those who view MoarVM as the new Parrot -- Parrot as it would have been if its implementation hadn't started until it was clear what Perl 6 would really need under it. (Aaaaaand without the technical or political fallout of "let's make a VM for ALL the dynamic languages!")
Aaaaaand without the technical or political fallout of "let's make a VM for ALL the dynamic languages!"
I remember Larry being really keen on that idea. The quote went something like "If everyone complains that CPAN gives Perl an unfair advantage, let's give everyone access to CPAN."
Why would I think that? I am aware of your recollections. I have read everything you blogged about the collapse of Parrot.
I have also read everything several other people wrote about the inception of MoarVM and the suspension of Parrot support, including key figures from both sides and several third-party observers. I have read the IRC logs of Parrot design meetings, including negotiations with the Rakudo leads, for the period leading up to the rupture. I have read key announcements by Parrot and Rakudo lead designers from earlier than this, wherein I think I see the seeds of the breakdown sown.
I made a detailed study of all this last spring, when I learned about the suspension. I have also been checking in intermittently on Parrot since 2002, and on every Perl 6 implementation I could find since the post-Pugs revival. And since last spring I have been kept aware of your position in particular through sundry comments here and on Reddit; you are a reliable presence whenever someone mentions Perl 6 or Rakudo without condemning it.
I can't speak to specific differences between my opinions and your recollections, since you did not see fit to say what those were. But I am hardly uninformed and I know of no error in what I said (viz., the actual words that I typed).
[1] If I wanted a document to make my point for me, I could hardly do better than the 2003 State of the Onion. Here's where Larry's head was in 2003: Yes, he thought a multi-language VM was just what Perl needed. He also thought that the Perl 6 design was basically done. He clearly didn't think there would be too much difference in kind between Parrot and the p5p runtime, as shown by his speculating that Ponie could be ready to support 5.10 and could entirely replace p5p by 5.12. He had not yet written the Apocalypse on the object system; its release in 2004 is really when it became clear how deep and structural the changes from 5 to 6 would be, and consequently it's also when it really became clear what a VM would need to provide to be good for Perl 6. Heck, in 2003 Larry thought "slow progress" meant a couple of major redesign documents a year, and he thought slow progress was just coming to an end. About the only thing that address was right about is that Larry didn't know very much. (Well, that and the switch statement.) If I'm saying reality disproved early conceptions about the realization of Perl 6, SotO 2003 is Exhibit A.
I think that's part of the problem--there are too many post-hoc justifications for why things happened the way they did that ignore what actually happened and why people made the decisions they did.
Dan's Parrot postmortem is still accurate: there just wasn't the will to turn P6 into a real, stable, shipping product, and there wasn't the honest acknowledgement that P6 wouldn't be a realistic replacement for Perl until far too late.
Admittedly, not everyone would define it as mainstream... but Tcl doesn't have a GIL and has had threading for a good, long time.
GILs are features of implementations, not languages; Ruby has implementations (most notably JRuby) without a GIL. And Clojure doesn't have a GIL, and seems to be approaching mainstream.
And Perl 6 isn't mainstream yet (it hopes to be, but then so do most languages.) And there's plenty of not-currently-mainstream dynamic languages without GILs in their primary implementations; many in the Lisp/Scheme family.
Initially it was used to extract tables from text documents, and its always had a strong focus on text manipulation and regular expressions.
Its implicit variables and syntax mean you can write very, very concise code. Yet by following stylistic guidelines of your choice, you can write code that looks sane and maintainable.
I really like the fact you can import os commands and call them as a part of the language. It makes writing scripts a breeze. In fact writing anything in perl is a breeze. Check rosetta code, you'll see Perl 6 is one of the most concise at every turn.
As much as I really like python, I find that calling system commands is a pain.. calling os.system is obviously far from great, and calling subprocess can get cumbersome.
I haven't played with perl in a while, but my past experiences with perl was always getting a lot done, with very little work.
I worked with Perl for 4 years, and while it's not the gauntlet of pain that people make it out to be, there were several annoyances (like needing to always hit the docs for that stuff).
What did you use it for, if I may ask? What how big a project are we talking about?
I would have thought hitting the docs wouldn't be a part of the annoyances list. Did you feel you had to hit the docs more than with any other language?
I understand it's a trade off. We don't have a large standard library in Perl like Python does, and that means there's a bit of searching required to find what to use, but that's often a benefit as well as a drawback. Would we have Path::Tiny if we had something that provided some but not all of the capability, and not as well? Would we have DateTime (or would it be popular) if we had a core DateTime-like module that was problematic, but mostly worked? Part of the beauty of having a small core set of libraries and an large and vibrant set of extended libraries is that the constant churn leads to newer and better things. Really what I'm lamenting, is that while there are these benefits to the churn, it still does lead to some painful situations where you find you've been using a poor choice for your needs just because you didn't know of the better choice that was out there. It's acceptable if it leads to DBIC, DateTime, Path::Tiny, etc, but it still sucks some times.
Having a LARGE core does as well, and mostly that any modules in the Perl core seem to also have their API and features frozen in time. Even if those features and API are not so good - it's in core! So, there's a reason to keep them how broken they are for backwards-compatibility sake.
I've also felt the burn of a core module that's then removed, and the new maintainer now going absolutely wild changing things. I understand exactly why they want to change things, and would not disagree with their ideas in a vacuum, but it causes great grief to me when I'm supporting apps that relied on in-core modules that have been upgraded out of core.
I wanna say that this problem is being used as a lesson for Perl 6 - that the core for the, "official/main/whatever" distro is going to be kept very spartan, but it's going to be encouraged to build upon that distro for your own Perl 6 releases. So, if you want the, "Web Framework" release, it'll come with all the bits and pieces you need to get that going - however editorialized that selection will be.
Moritz talks about this concept, here:
http://perlgeek.de/blog-en/perl-6/how-core-is-core.html
Although this post is pretty old, and I'd hate to say that their line of thinking now.
Have a look at the 'sh' python module to ease your pain: http://pypi.python.org/pypi/sh
For me the greatest advantage of the Perl5/shell integration is that you can use Perl's sane data structures, flow control, and code organization features instead of their bash equivalents which have endless pitfalls and can be less portable than basic Perl5.
To me the most unique aspect is Perl 6's unicode string handling which is probably the best unicode support of any language out there. I could see it catching on in niches that need to do heavy cross-characterset text processing.
Some things I found interesting (in addition to what s_kilk mentioned and linked to and others have already mentioned some of them) * Gradual typed! * Multi subroutine * Hyphen in variable names * @numbers.=sort * .WHAT * Catch blocks * .defined * Unless
It will be fun :)
I however don't understand the reason for the naming of eg elsif, my, slurp/spurt?? (instead of else if or local or fread/fwrite) Is it a perl culture thing? Because they mention in the tutorial that Perl 6 belongs to the C-family languages (and then call the "for" loop in C "loop").
Yes, it's for historical reasons. "elsif" is spelled that way in Perl 5. Perl 5 has both "my" and "local" to specify lexical and dynamic scoping, respectively, so Perl 6 using "local" for lexical scope would be confusing. "slurp" is a common term for reading the entire contents of a file at once.
It's available as long as the declaration stays on the call stack. It more-or-less allows globals to be temporarily redefined.
my is Perl 5, is different than local, and is gloriously short. Nicest way I've ever seen to declare a variable. :)
slurp/spurt are routines to read/write an entire file at once. slurp is pretty standard in other languages, I believe, and spurt was chosen to be a natural opposite to it. Perl 6 still has open / close / read / write, etc. Though to be fair, honestly I usually use lines, which (with no other arguments) gives you a lazy list of the lines in standard input / files specified on the command line.
for in Perl 5 was some weird combo which could be iterating over an array or a C-style for. In Perl 6, those have been separated. Because iterating over an array is vastly more common, that gets the shorter keyword. The C-style loop got the loop keyword.
I like even more that you can mix static and dynamic typing, so to speak. After taking their sweet time, I am not overly confident about adoption of Perl6, but I hope I'm wrong.
At least, from what I can tell so far, Perl6 manages to keep the spirit of Perl, while fixing a number of things that were wrong, or at least problematic, in Perl5.
I want short examples, brief explanations of those, and then some problems to solve.
Wow. This will make a few people happy who think underlines and camel case are ugly.
What is a mis-feature is you can't assign-create to these variables when they're part with sigil-bearing variables, so, for example, here I ended up using a sigiled-Δ, which isn't as pretty :) https://github.com/zoffixznet/perl6-Color/blob/master/lib/Co...
Fwiw you can assign to such "raw" nouns if you declare that the raw noun you're declaring refers in turn to a rw container. For example, a plain `$` is a container (an anonymous Scalar):
my \Δ = my $ = 100;
Δ = 200;
my \array =@= 1,2,3; array[2] = 200; say array;
[1 2 200]It can be mis-applied. It arguably has been mis-applied in this example. But I can also argue it the other way. It depends on whether the intro's goal is to address overly simplistic general criticisms ("sigils are ugly and unnecessary!") or to inculcate mature understanding from the get go.
Sigils denote the nouns of the language. They are there for your benefit,not the compiler's.
Kebab notation makes sense in other contexts, like DOM IDs and CSS class names. It does not make sense in a case like that.
* Strings that are made of Unicode grapheme clusters instead of codepoints or bytes. This means that a substr() operation for example can't even accidentally rip a apart a base character and a combining character on top of it
* Grammars as a language feature
* Gradual typing
* A built-in meta object protocol
* Concurrency based on high-level primitives (promises, queues, supplies, ...) with syntactic support (instead of threads and locks; which are still available if necessary, but discouraged, because they don't compose well).
* Lazy lists
Its power is amplified by the part Perl 6 regexes are better than anything there is out there.
Even better, this extends beyond ASCII and applies to Unicode too. And will work with other powerful control structures.
I'd fix that date to something like 2027.
For eg. See the parse dialect which is a TDPL that comes with Rebol / Red
- http://www.rebol.com/docs/core23/rebolcore-15.html
- https://en.wikibooks.org/wiki/REBOL_Programming/Language_Fea...
- http://www.red-lang.org/2013/11/041-introducing-parse.html
"... POSIX doesn’t promise you’ll get UTF-8, or even ASCII. It promises ... a bunch of bytes. We can now cope with this properly – surprisingly enough, thanks to the power of NFG. We now have a special encoding, UTF-8 Clean-8-bit, which turns bytes that are invalid as UTF-8 into synthetics, from which we can recover the original bytes again at output. This means that any filename, environment variable, and so forth can be roundtripped through Perl 6 problem-free. You can concat “.bak” onto the end of such a string, and it’ll still work out just fine."
From https://6guts.wordpress.com/2015/11/21/what-one-christmas-el...
One that has caught my fancy are various uses of the "Whatever Star". This appears as a * in a few contexts. In many it is really a shortcut for the "Whatever" class, so you can use it in function signatures to enter sort of "automatic mode".
@shuffled_names = @names.pick(*) # randomly pick... however many you have. whatever.
@nums.map(*/2 + 3) # expression-lambda from context around a whatever-star
@nums.map( -> $n { $n/2 + 3 } ) # equivalent with a real stabby arrow lambda
@nums.map( { $^n/2 + 3 } ) # $^n is a generated alphabetical-positional argument
In Perl 6, detecting that an operand is "missing" isn't possible due to the existence of prefix/infix/postfix operators with the same names, so it expects a "whatever" star in place of the missing operand... :)
For Perl-folk, there is a module to convert between POD and Asciidoc:
http://valbonne-consulting.com/job/perl-or-lua-software-deve...
I see nothing new here. But I must say that Perl 6 seems to be easier to learn than Perl 5 for beginners.
The magic is in the more advanced parts of the language. The, "hard things should be possible" parts.
For example, in Perl 6 a character at the language level is a grapheme. This is per a proper understanding of the Unicode standard. It seems that most folk (and language designers/designs, including eg gvr/py3) don't/didn't realize that Unicode always intended graphemes as the obligatory ultimate destination for modelling "characters" and providing truly clean Unicode text handling. (Swift has attempted the same thing but their current character iterating implementation and API are clearly inappropriate long term for a performant text manipulation focused language so they'll surely have to redo that part of Swift over the coming years.)
Another example is the parallelizing, async, and concurrency features in Perl 6. These are all surprisingly simple to use and performant but took a lot of design talent, and engineering talent under the hood, to get right internally and simple externally.
Sticking to positive stuff for a moment longer, some features bring important concepts from decades past in to this century. Most notably, afaict, Perl 6 provides a universal unrestricted grammar[1]. Aiui this could put help put "string rewriting", a relatively neglected mathematically proven isomorphism to the lambda calculus and turing machine models of computation, back on the map. It will be interesting to see what happens as Perl 6 matures.
The biggest downside I see, beyond widespread negative associations with the name 'Perl', is immaturity. Perl 6 has lots of bugs, poor doc, is currently slow as molasses for a lot of stuff, and so on.
* Grapheme-level string processing, even when there's no pre-composed Unicode codepoint for the grapheme. I think Swift is now doing this, too, but I'm not sure if anyone else is.
* Perl 6's grammars are to an extension of parsing expression grammars what the regular expressions in Perl 5/Ruby/JavaScript/etc. are to an extension of regular expressions. One can use PEGs (or other grammar formalisms) in any language with a library or code generator, but, with a few exceptions like Parsec, it's usually not nearly as convenient.
* Roles, similar to the traits concept developed by Nathanael Schärli, Stéphane Ducasse, Oscar Nierstrasz, and Andrew P. Black (and present under that name in e.g. Squeak Smalltalk and PHP since 5.4). Roles/traits are similar to mixin-style multiple inheritance, except that, when including multiple traits with conflicting methods, the including class must explicitly resolve the conflict. Mixin-style systems use an implicit linearized method-resolution order, which is more fragile because newly added methods in earlier mixins can silently override methods of the same name from another mixin that the caller was actually intending to call.
* Multiple dispatch is not unique to Perl 6, but it's not especially common, and it's very convenient.
* Configurable object representations. For example, a class can be defined to use the default P6opaque representation, which is I think usually implemented as a pretty standard struct-like representation with properties at fixed offsets. Other possibilities might be a hash table representation, where an object is represented by a hash table and attribute access is done by accessing the values of appropriate keys in the hash table. If one wants to forgo the optimizations allowed by fixed representations, one can even define a class with `is repr(*)` to allow individual objects of the class to be created with different representations.
1: http://design.perl6.org/S04.html#Phasers
2: https://en.wikibooks.org/wiki/Perl_6_Programming/Lazy_Lists_...
3: http://design.perl6.org/S05.html#Grammars
4: http://design.perl6.org/S03.html#Binary_hyper_operators
5: http://design.perl6.org/S12.html#Types_and_Subtypes
6: http://design.perl6.org/S12.html#Multisubs_and_Multimethods
Languages become part of the standard installation by having very commonly used toos written in them.
I might be wrong, but I'm pretty sure ruby isn't part of a standard Debian installation, and neither is lua, for example. Ruby is very popular for web apps, but you don't need web apps to boot the computer, start a GUI and install packages, so it's not part of the standard installation.
But it's only an 'apt-get install ruby2.1' or so away, and so is rakudo (the current Perl 6 implementation). The debian package in stable is outdated, but work on newer versions is in progress. (Don't know about CentOS, sorry).
We could very well have asked what was the use in learning Go in 2010, but look how that turned out.
Perl6 is currently a very interesting language with a relatively weak module ecosystem. Which is a position many languages have been in before.
Let's not dismiss it out of hand.
I always thought that would make a world of a difference.
Here is a gist where I'm calling out to some Python. It is not done in the magical future way (which is in progress) of just doing "use matplotlib::pyplot:from<python2>" or similar, but not too bad.
https://gist.github.com/awwaiid/ef3f0abcfa96e34977b4
(I wrote this some months ago -- it can be a bit cleaner now)
Perl, more than any other language I know, sacrifices nearly every other property in the name of being useful. It's not a conceptually clean language, or an elegant one, or a simple one, but if you need to get stuff done, now, there is very little that can compete with it. (At least for some rather specific values of "stuff" - Perl, IMHO, really shines at small-ish scripts that need to convert data from some format to another, or merge data from different sources, especialy when lots of text-handling are involved). Parsing a log file, or matching user accounts from a Windows domain with employee records in an ERP system's database are two examples that come to mind because I had to do those things not too long ago.)
Perl 5 has problems though, especially when it comes to writing large-ish programs. While you can write readable und unreadable code in any language, Perl makes writing unreadable, unmaintainable code easier than, say, Python. Perl 6 tries to fix a lot of this while remaining as useful as Perl 5 (or at least trying to).
Another factor that mattered back during Perl's heyday was the insane lengths it went to for maximum portability. The Perl porters shouldered the burden of making it run on DOS/Windows, Mac OS, VMS, and all the weird Unices that existed at the time. This doesn't matter as much nowadays, but it was crucial back then.
If you had a text-munging or scripting problem, and wanted to solve it once and for all, Perl was the perfect tool.
Perl lets you pretend that Windows know how to fork. That alone still amazes me in a way.
During my training, I had to set up BIND 9 on IBM mainframes running z/OS and configure TSIG (cryptographically verified zone transfers), which among other things required changing the (shared) keys on a regular basis (about once per month, I think) and distributing them across about half a dozen systems. Fortunately, at that precise point in time, I stumble across a news headline that IBM just released Perl 5.8 for z/OS and managed to get the sysprog to install it.
The alternative would have been REXX. I looked at it, quickly, and then looked away, very determinedly. I was really glad Perl was available on those machines.
On the other hand, there's an equally strong argument to "pick the right paradigm for the task". It's taken me many years to appreciate the elegance in that approach, as it requires a thinking in multiple models at the same time. On a totally subjective note, I find it more "human" as our creativity lets us what's suitable for the task, without trying to mold everything into the same uniform mold. That may appeal to certain personalities more than others.
Currently, I am also using a monitoring tool called Argus (http://argus.tcp4me.com/) which is completely written in perl. It doesn't seem super well maintained, but I really like it, so I have been reading through the source and have been thinking about doing something similar in Elixir, but Perl6 would be a perfect update for it.
Perl is largely a sysadmin tool, in that many of us sysadmins are not formally trained in programming, but we often need to get shit done, and perl enables that. When bash, awk, and sed start to falter, we tend to use python and perl, so that's another use case. Simpler syntax and better threading would certainly help with that.
- Subjective, but in my experience, the Perl community is more full of smart yet practical people than any other dynamic language community I've participated or dipped my toe in (and most popular static manifestly typed language communities to boot). I don't say this to trash Ruby or Python (or even JavaScript and PHP, which have plenty of smart users and participants); I just mean that I often learn more from engaging with the Perl folks.
- Kindof a corollary, but Perl 5 seems one of the few places where industry's reflexive treadmill dash towards the newly-formed but usually isocapable turned into a careful reflection on using the existing power at hand wisely and the best marginal gains from key additional features.
Place two jobs in front of me, one of them working on a new Go project, the other on a new Perl 5 project, my bet is going to be that the latter would be part of a more satisfying overall experience.
Now, Perl 6, this is starting to look like a language where they are going to make a number of things easy that most programmers didn't even know were hard, a number of things possible that most programmers didn't even know were possible, where recent PL research is going to meet further practicality, where unicode might even actually be reasonably comfortable to work with.
https://hub.docker.com/_/rakudo-star/
And its GitHub repo: