The first fully functional Ruby compiler

It's a glorious day. The JRuby compiler is now complete and functional. Without sacrificing interpreted mode. Read more in Charles blog, here.

SQLServer is also stupid

I can't understand the problems database drivers have with whitespace where there shouldn't be any. It's clearly wrong...

So say that you create a table in SQLServer that is nullable. If you use DatabaseMetaData and do getColumns for that table, and check the nullable column, and fetch the value at index 18 - IS_NULLABLE. What you get back here is "YES" which is all according to the API. But if you by chance do the same thing for a column that is non-nullable - what value would you get then?
"NO ". Notice the space. Lovely. I *heart* databases.

... Someone asked me in response to my last blog post which database I would choose if I could. Hard question. I'd rather do without databases. But if I have to, I'd go with Mimer SQL which is probably the most SQL-compliant database ever, and really doesn't have WTF moments at all. It's small, it's from Sweden, and it's very nice.

Oracle is stupid

I've just spent two days debugging and fixing AR-JDBC issues with Oracle. And let me tell you, those days haven't been fun. I am really unfond of Oracle at the moment. You probably saw my last post. Now, let me add a new point of insanity to the proceedings...

Say that you define a table like this:

create table companies (
  firm_id integer default null references companies
);

Now, if you try to get the default value of the column firm_id in some manner (for example, you could use JDBC, DatabaseMetaData.getColumns, and getString(13) on the result). You could also use the OCI8 C interface. You would get the same result. Any guesses? What is the default value of the column firm_id? Some might say that it should be the String "null". Nope. It's the String "null ". Notice the space.

Now, if you instead defined your table like this:

create table companies (
   firm_id integer default null
);

In this, what is the default value of the column firm_id? it's "null". Without a space. Yes, it varies. Yes, it actually varies based on the formatting of the SQL used to create the table. You could potentially use the Whitespace language to embed arbitrary programs in the null default value... Because if there is two blanks between the null word, and the next token, then that's what you will get from the default value. Notice that we used two totally different interfaces to get this information so it's obviously something that is saved in the database engine. Wow.

Is this insane? Is it crazy? Am I thoroughly disgusted by now?

Yes. And also, AR-JDBC finally runs all ActiveRecord tests with Oracle.

Lovely intermittent Oracle XE problem

I'm working on AR-JDBC support for Oracle. The easiest way to do this for me is to run Oracle XE inside Windows XP in Parallels. That works fine. Except for this dreaded message that started showing up and killing all my efforts: “ORA-12519, TNS:no appropriate service handler found”. I love Oracle error messages. They are so incredibly helpful!

At least in this case I found a solution to the problem on da Internet. I'm writing this blog post to make the information more obvious to Google.

It seems there is a bug in Oracle XE in the monitoring of processes that manifests this way. Nice. But you can fix it! Just open up your SQL console, write "connect system", submit your password and then write "ALTER SYSTEM SET PROCESSES=150 SCOPE=SPFILE;". After that, remember to restart the listener. And everything should be joy again.

Can bytecodes perform well?

I really need to write an answer to a comment that appeared on my post about Rubinius by Kragen Sitaker. It has two points in it, and I really want to address one of them at some length. So here goes. The comment read like this:

"It is byte code based. This means it's easier to handle performance."

If by "handle" you mean "not have".

"garbage collection/object memory can be switched out to use another algorithm"

In your dreams. I suspect you'll find out that the architecture isn't as clean as you think it is when you try to plug in some other existing garbage collector or object memory.

It sounds like a good project, but I don't think its advantages are going to be so enormous as you think they are.

Woha. That's hard to argue with. Isn't it? Or maybe not. Let's being with the second point. Is Rubinius architecture clean and decoupled enough to allow swapping of GC and object memory? My answer is a resounding yes. But of course you can go and look for yourself. Of course, it's possible to make a system where you can decouple the GC. Sun's standard JVM does this, for example. But the interesting point isn't whether Rubinius' hooks for this is clean enough, but if they are cleaner than MRI's. If you have ever tried to switch out the GC in MRI, you know that Rubinius beats MRI hands down in this regard. If not, you can ask Laurent Sansonetti at Apple, who have actually done most of the work to switch out the GC in MRI if that was a fun experience.

Let's see, what's next? Oh yeah. Bytecodes are always slow. No argument here. C++ will always beat a bytecode based engine. And C will almost always beat C++. And assembler (in the right hands) will usually beat C. But wait... Isn't Java bytecode based? And doesn't Java 6 perform on the same level as C in many cases, and in some cases performing better than C? Well, yes, it does... And wasn't Smalltalk always based on bytecodes? Most Smalltalk engines performed very well. Why is MRI switching to bytecodes for 1.9? And why has Python always been bytecode based? And why is the CLR bytecode based? Why was even Pascal using bytecodes back in the day? (OK, that is cheating... Pascal used bytecodes for portability, not performance, but it still worked well in that aspect too). Erlang is bytecode based.

Basically, there are some cases where a static language will benefit from straight compilation down to hardware machine codes. OCaML is a typical example of such a language. Due to the extremely stringent type requirements of the language, the emitted code is usually faster than C. But that is the exception, and only works for bondage-tightly typed languages. When talking dynamic languages, bytecodes is the real path to good performance. Granted, a naive implementation of a bytecode engine will not perform well. But that is true for a compiler too. The difference is that the part interpreting bytecodes is usually a quite small part of the whole runtime system, and it can be switched out for better performance, piecemal or all together.

There are other reasons. For example, statically typed languages like Java and the CLR family of languages use bytecodes because it gives the runtime system the opportunity to dynamically change the machine code running based on statistics and criteria found out during runtime. This means that your application will actually have better performance in the parts where it counts, and the parts that are not heavily used will not be optimized. (That's what HotSpot does, for example). This is not possible in a clean compilation to machine code. Java would never have had the performance it has now if it weren't for the bytecodes.

So please, stop spreading this myth. It is NOT true and it has NEVER been true.

Rubinius is important

I predict that parts of this blog posts will make certain people uncomfortable, annoyed and possibly foamy mouthed. If you feel that you're of this disposition, please don't read any further.

As I'm working on JRuby, I obviously think that JRuby is the best solution for many problems I perceive in the MRI implementation currently. I have been quite careful to never say anything along the lines that JRuby is better than anything else, though. I will continue with that stance. However, I won't restrict myself in the same way regarding Rubinius.

In fact, I'm getting more and more convinced that for the people that don't need the things Java infrastructure can give you, Rubinius is the most important project around, in Ruby-land. More than that, Rubinius is MRI done right. If nothing substantial changes in the current timeline and plans for Ruby 1.9.1, I predict that Rubinius will be the CRuby implementation of choice within 6 months. Rubinius is an implementation done the way MRI should have been. Of course, Matz have always focused on the language, not the implementation. I'm very happy about that, since it means that we have an outstanding language.

But still. Rubinius will win over MRI and YARV. I've had this thought for a while, and I'm finally more or less convinced that it's true. Of course, there are a few preconditions. The first and most important one is that Rubinius delivers 1.0 as planned, by the end of the year and that it doesn't have abysmal performance. Or if YARV would happen to be totally finished and perfectly usable in the same time frame, things might take a different turn.

Why is Rubinius so good, compared to the existing C implementations? There are a number of good reasons for this:

• It is byte code based. This means it's easier to handle performance.
• It has a pluggable, very clean architecture, meaning that for example garbage collection/object memory can be switched out to use another algorithm.
• It is designed to be thread safe (though this is not really true yet), and Multi-VM capable.
  
• It works with existing MRI extensions.
• Most of the code is written in Ruby.
• It gives you access to all the innards, directly from your Ruby code (stuff like MethodContexts/BlockContexts, etc).
• The project uses Valgrind to ensure that the C code written is bullet proof.

Anyway. I put my money on Rubinius. Of course, that doesn't mean I don't think JRuby have a place to fill in the eco system. In fact, the real interesting question is what will happen when both Rubinius and JRuby have become more mature. I'd personally love to see more cooperation and sharing between the projects. Not a merging, since the goals are too separate, but it would be wonderful if JRuby could use the same Ruby code for all the primitive operations as Rubinius does.

Right now we have a simple Rubinius engine in JRuby, that can interpret and run some simpler byte codes from Rubinius.

JRuby and Rubinius are both extremely important. Right now I believe JRuby is more important, since it opens up a totally different market for Ruby, and gives the benefits of Java to Ruby. Rubinius has another place to fill.

Of course, being who I am, I have also looked into what would be required to port Rubinius to Java, using the same approach directly instead of going through JRuby. If you decide to use Java's Garbage Collector, Java Threads, and reuse the JRuby parser you would end up with about 40 files of C code to port. Most of these are extremely easy, and none is really that hard. And what you would end up with is something that would run the same things Rubinius does, but with the possibility of invoking Java code at the same time. (Of course, I hope that Evan reserves a block of about 8-16 bytecodes that can be implementation dependent - these Jubinius would use to interop with Java code).

Ruby+Erlang concurrency?

I keep reading from lots of people that you can't bolt Erlang's concurrency model on Ruby. But is this really true? MRI already has green threads. Adding a higher level of concurrency with the basic primitives of !, recv and spawn doesn't seem like a gigantic project. The main problem would be to prohibit access to shared memory between the spawned green threads, and avoid the GIL. But that doesn't seem to be that large of a problem. The main question is rather if this model would fit well with the Ruby language... Since Erlang was designed from the ground up with these primitives in mind, many of the libraries and functions work well with it. For example, pattern matching work exactly the same in recv as in function dispatch or case expressions.

On the other hand, the send, recv and spawn primitives in Gambit Scheme seems to work out really well even though the language is LISP in root (or maybe that's the reason?)

In fact, this is one of the few places where it would be harder to add something to JRuby than MRI. Since we can't control the full stack it would be very hard to implement anything resembling Erlang processes in Java. And Java threads would almost certainly be too heavy weight for this to work. Hmm.

Practical JRuby on Rails released!

Today my book Practical JRuby on Rails has been released by APress. It has got two forewords, one by Martin Fowler and one by Pat Eyler. And you can order it right now from Amazon here. Hopefully it will also be available in your closest computer book store!

What about Sun's Ruby strategy?

Wow. Today was a strange day for blog reading. I've already had several WTF moments. Or what do you say about 7 reasons I switched back to PHP after two years on Rails, where the first and most important reason seemed to be

IS THERE ANYTHING RAILS/RUBY CAN DO THAT PHP CAN’T DO? … (thinking)… NO.

Bloody hell. All programming languages in use today are Turing complete. Of course you can do exactly the same things in all of them. But I still don't program in Intercal that often.

Example number two: About JRuby and CPython performance. This blog post uses the Alioth language benchmark to show us that Python's C implementation is faster than JRuby. Of course, the JRuby version used in this comparison is 1.0, which is now almost 4 months old. Comparing the C implementation of one language with a Java implementation of another language seems kind of suspect anyway.

But these two examples is nothing compared to a post by Krishna Kotecha from yesterday. It's called Sun's Ruby strategy - Engage and Contain?. You should ge read it. It's actually quite amusing. I usually don't respond to other blog posts, and I don't usually quote in my blog. I'll do an except here, because there are several points in that post I want to elaborate on.

Compromise definitely seemed to be an underlying theme at RailsConf Europe. DHH’s keynote downplayed the need for evangelism - something I strongly disagree with. Rails has certainly made a lot of progress towards wider acceptance, but we’ve got a really long way to go before more companies start to adopt it, and I certainly don’t think turning down the evangelism and doing stealth deployments via JRuby is the answer.

There are really two interesting points in this paragraph. First of all the question of evangelism. I would say it's about time to turn it down. Actually, I've gotten the very real impression that the wild-eyed Rails evangelism is now turning people away from Rails rather than winning more "converts". Telling people about the advantages of Rails is still something that needs to be done, but the full fledged Rails marketing machine has already done it's work and should be turned down a notch.

The second point Krishna sneaked in there is about JRuby "stealth deployments". I'm pretty sure no one will ever do a real stealth deployment, and I find that concept totally wrong.

At RailsConf Europe 2007 however, Dave didn’t even specifically discuss Rails - and this seems to have been at the behest of the conference organizers. If this is the case, then the Rails community is already in trouble. Is this the price of Sun’s ’support’: that the community is no longer able to freely discuss the platform and what work needs to be done to get it accepted in the enterprise on its own terms?

Where does this particular conspiracy theory come from? Is there any evidence whatsoever that the organizers of RailsConf wanted Dave to not speak about the shortcomings of Rails? And even if that were the case, what's there to say that Sun is the reason for this? (Couldn't it have been IBM or ThoughtWorks, who were also Diamond sponsors?)

I have real problems with this attitude and approach. Selling Rails and Ruby, as “just a Java library” is a massive disservice to the technology, and simply means enterprise customers and decision makers won’t evaluate Ruby on its own merits.

What is important to realize is that the argument "just a Java library" will only ever be used in the case of organizations where there are good technology arguments for using JRuby on Rails, but non-technical management are making decisions based on what is most safe at the moment (see the Blub Paradox by Paul Graham). In most cases the "just a Java library" argument is useful only when talking about conservative environments who are standardized on a certain platform. And believe me, Krishna, there are many places where Java is the only allowed technology to be deployed. But in most cases JRuby will work fine for those IS departments. Is it really a disservice to the technology to make Rails and Ruby into something that can be used in even wider domains, removing cruft and bloatware at all places possible? Is it a disservice for the technology to be used in places where it would never enter without the help of JRuby?

But JRuby is not the best answer for Rails and Ruby developers.

I don't really understand this quote. Obviously Krishna have strong opinions about the subject, but stating something as a fact without telling the reasons for it being that way doesn't feel that interesting.

Serious Rails deployments (Mongrel not some Java Application Server) within enterprise environments may be difficult to achieve, but with the right political backing and developer persistence it can be done.

I must say I find it interesting that Mongrel is viewed as a serious deployment option when compared with a standard Java application server. The question here isn't how we should get enterprise environments to use Mongrel; rather, we should first decide if Mongrel really is a serious enough deployment environment for enterprises.

And this will benefit the whole Rails community - not just those who tie themselves to Sun’s technology platform.

I heard this rumor about Java being Open Source... Does that still mean tying yourself to "Sun's technology platform"?

And also, the vendor with the most to lose if Rails really does fulfill its potential in enterprise environments.

Why? What exactly does Sun lose if Rails win? Sun is using Rails and benefiting from it. And be careful about this: Rails is Rails, no matter if it runs on JRuby, MRI, YARV, Rubinius, IronRuby, Ruby.NET, XRuby, Cardinal or any other Ruby implementation now or ever. Rails is Rails.

Maybe I’ll start to believe when they start promoting Ruby on Rails at JavaOne, as opposed to promoting JRuby on Rails at RailsConf.

I guess you didn't attend JavaOne 2007, where both JRuby on Rails and Ruby on Rails had sessions, including promoting in one of the major keynotes. Sun is serious about Java being a multilingual platform. Of course they're spending money on getting these languages working on Java, but Sun is also giving support to both Rubinius and MRI. Would they really do that if this conspiracy theory is correct? For more information about that particular data point, take a look at Tim Bray's blog here: Rubinius Sprint.

Much more likely I think, is that we’ll see a Java based Rails alternative that ships with some new version of Java which has been designed to incorporate features from dynamic languages like Ruby and Python.

Java will almost certainly never ship with a web framework. That said, Phobos is one of the Sun projects for web development that uses JavaScript and incorporates features from Rails and Ruby, and also Python and other languages and frameworks.

And still, Sun doesn't seem to have a problem with Rails and Phobos living side by side. GlassFish includes support for both. And the Rails support doesn't make any changes to Rails, it doesn't require you to do anything extra, except that your application should run in JRuby. The latest version basically allows you to say "glassfish_rails start" while standing in your application directory.

...what compromises are we making for Sun’s involvement...

Yeah. What compromises are we making for Sun's involvement in the community? Except handling the fact that we get more commercial backing, more money in the ecosystem, more help from Sun engineers creating high quality Ruby code, a server that happens to host the SVN server for Ruby itself, and so on? Are these contributions? Sure. Are they commitments? Yeah. Are they something that will require compromises from the community? No, not really.

Sometimes I think that many in the Open Source world still panics as soon as a big company starts to make inroads. And yes, in many cases this hasn't worked out well. But we gotta see to the facts too. Some companies we will never be able to trust, but Sun has definitely been on the right side of the Open Source fence for a long time. Come on, people.

RailsConf Europe recap

I am finally back from a week of travel. Funny, it feels like much more than a week - but I guess that's because there were some interesting mishaps with some of the flights.

Last Sunday I traveled to Berlin to attend RailsConf Europe. I arrived kind of late and was really tired and out of it during the Monday. I didn't find most of the tutorials going on that enlightening - though it was fun to see David, Aslak and Dan present on RSpec together. I liked the mind map format they used instead of regular slides. Due to general tiredness and a really bad migraine I went to bed early. But before that I managed to see Dave Thomas introductionary keynote. It was interesting and extremely well presented; the theme was art and how it can help you as a programmer to use this metaphor to understand the things we do more closely. I didn't find anything really new in the presentation and I've heard several people say that they would prefer if Dave had spent some time talking specifically about Rails instead. I tend to agree.

The second day of the conference was really good. DHH delivered a keynote that basically said that there is nothing really new happening with Rails. After that it was time for sessions. I guess none of the first presentations made any real impact on me, since I don't remember what they were. After lunch I saw Nic Williams talk on meta programming; the talk was really fun. I didn't learn anything new, but I had a fun time while doing it.

Charles and Tom did their JRuby presentation. And I also saw Evan Phoenix Rubinius talk. It was very interesting - if I could stand programming in such a low level language as C, I would probably spend more time helping them than I do now. I will write more about Rubinius - probably tomorrow - I haven't really said everything I need to say here.

After the sessions there were more keynotes. Roy Fielding talked about REST. I gotta admit I didn't really hear much of it though, since I was spending time fixing an annoying bug. After that Craig McClanahan talked for a few minutes about Rails. It was very enlightening to know how well regarded Rails is within Sun. Some people seems to have a different view on all this though, seeing conspiracy and dirty dealings in the way Sun is working Rails. I'll need to cover that in a separate blog post too.

ThoughtWorks threw a party after the days session. That was very fun and well attended.

All the JRuby team attending (Charles, Nick, Tom and me) gathered together on the evening and did a JRuby Q&A BOF. Lots of people there, and a very free form of presentation made this one of the highlights for me. I had great fun and I hope the audience did too.

Finally the Wednesday... Cyndi Mithell from ThoughtWorks did a very nice keynote about why Ruby and Rails may be ready to cross the chasm and get a strong hold in the enterprise.

Koz and Marcel did a very good Rails Best Practices session. Down to earth, simple, totally useful advice on things to avoid in a Rails application and what to do instead.

And then it was time for my presentation about JRuby in ThoughtWorks. I think it went very well, but it became a little bit too corporate for my taste. I'll need to make sure that doesn't happen the next time. Maybe some more code in the presentation? =)

Most of the rest of the day was spent networking, hanging out in the exhibit hall and stuff like that. And then RailsConf was over.

My flight to Sweden from Berlin that evening didn't really happen as I had expected it too. Instead I had to spend the night on a hotel in Frankfurt and take an early flight from there to Gothenburg.

Overall I had a very good time at RailsConf this year. It's a worlds difference from RailsConf last year in London, which I felt was a real waste. This year the energy was high, much interesting things going on and lots of nice and smart people. Not as good as RailsConf in Portland earlier this year, but still very well worth attending. It seems that RailsConf has found a good balance in sessions. The only thing I can wish for would be more interesting choices for the tutorial day.

Ruby-DBI and JDBC

Last week I decided it was time to get Ruby-DBI working with JDBC. I resolved to get on it since it would be highly useful and probably not so hard either. But as it turned out I didn't really need to do anything. The work has already been done by Kristopher Schmidt. Very nice. So instead, this post will detail how to get it working with JRuby.

First download the Ruby-DBI distribution from RubyForge. Secondly, unpack. The third step is to configure and install it. Execute these commands inside the Ruby-DBI directory:

jruby setup.rb config --without=dbd_sqlite,dbd_sybase
jruby setup.rb setup
jruby setup.rb install

Now you should have Ruby-DBI installed, but no DBD drivers. Verify that it's actually installed by running "jirb -rdbi". The next step is to install the JDBC driver. First create a directory called $JRUBY_HOME/lib/ruby/site_ruby/1.8/DBD/Jdbc. Download Jdbc.rb and JdbcTypeConversions.rb and put them into this directory. Also make sure that the JDBC driver you want to use is on your CLASSPATH. Now you can create a script like this:

require 'dbi'

DBI.connect('DBI:Jdbc:mysql://localhost/test', 'test', 'test',
                 'driver'=>'com.mysql.jdbc.Driver') do |dbh|
p dbh.select_all('SELECT * FROM a_table')
end

Make sure that you include the name of the driver as done in this code. The first parameter should be the regular JDBC URI with DBI: first. In this case it's the test database on localhost I connecting to, using the test username and test password. More information about how Ruby-DBI can be used can be found by Google.

nXML in earnest

So, for various undisclosed reasons it's time to start seriously hacking XML. Now, the end artifact of this will be one of the few situations where XML is actually justified and makes this process better.

Of course, Emacs is a must for this challenge. I wouldn't even try doing it without a real editor. Now, the undisputed king of XML in Emacs is nXML-mode. I want it everywhere. So the first step is to bring out Trang and convert all DTD's into RelaxNG. Then edit schemas.xml and we're running. Well, except for the simple fact that Emacs refuses to load anything else than xml-mode automatically. That sucks.

So after lots of looking, it seems there is a new magic-mode-alist that can look at the beginning of a buffer and "magically" decide what kind of buffer we're dealing with. For some reason this behavior overrides my carefully laid out auto-mode-alist. Well. The solution for all you people is simple. Just add this snippet late in your loading process:

(setq magic-mode-alist
   (cons '("<＼＼?xml " . nxml-mode)
            magic-mode-alist))
(fset 'xml-mode 'nxml-mode)

JavaScript ignorance

Put it down to my general ignorance - I've never realized that JavaScript has send/perform, and has had it for a long, long time. Of course, it only works for methods that exists on the object. Or? Is there any way of capturing non-existent method-calls/property look-ups like method_missing does?

Anyway, send:

function SendTester() {}
SendTester.prototype.foo = function() {
   print("Hello");
};

new SendTester().foo();
var name = 'foo';
new SendTester()[name]();

Please, tell me something more cool I've been able to do in JavaScript in browsers for 5-10 years but didn't know about!

Concurrent DSLs

With all the current talk of DSLs and concurrency, what I find lacking is discussions about how to combine the two. Of course, domain specific languages are incredibly important - they create a logical separation between the implementors of the business logic, and the people implementing the actual implementation of the DSL. Does it seem like a strange idea to want many DSLs to be able to run parallel to each other? I would imagine that in most cases a DSL that describes business rules and business logic is sequential in the particulars, but that there are also larger concurrency possibilities. This should be totally invisible for the business rule implementor in most cases - the runtime system should be able to run everything as efficient as possible.

A natural way of looking at DSLs is as declarative languages. In many cases that's the way you write them (just look at the ActiveRecord API. it looks very declarative - it just happens to be implemented using imperative primitives). Now, if the language is truly declarative it should be side effect free. In the end, that isn't a real goal, but if it would be possible to clearly understand which parts of the rules are using side effects, the rest of the implementation should be able to run totally concurrently.

These kinds of things should be possible to implement in any language with sane multi threading/multi processing. That said, I wouldn't want the task of doing it with Java's concurrency primitives if I can help it. So what kind of tools would be helpful? Possibly Erlang of course, since it's already functional and that makes the identification of side effects much easier. Another possible alternative seems to be Gambit Scheme and Termite.

Anyone else thinking about these issues? Is there any research going on that would shed some light on it? And further, what's the next step? Why haven't this question already been discussed? It seems to be well time for it now.

Should Ruby have optional typing and compiler directives?

I'm starting to miss a few Common Lisp special forms more and more. To be more specific, I miss the family of declare/declaim/proclaim. I think a version of them could actually be extremely useful for Ruby. The current approach to String encodings in 1.9.1 uses a "pragma" inside of a comment on the first line of a Ruby file, like this:

# coding=utf-8

This works fine for coding, I guess, but I would like to have something more general - something that can be used inside of code too. As a typical example of the kind of thing I would love to be able to do, here is an example of a Common Lisp implementation of fib:

(defun fib (n)
(cond
  ((or (eql n 0) (eql n 1)) n)
  (t (+
      (fib (- n 1))
      (fib (- n 2))))))

As you can see, it's the standard implementation. But, after this implementation is finished, I can continue by adding declarations:

(defun fib (n)
(declare (integer n))
(cond
  ((or (eql n 0) (eql n 1)) n)
  (t (+
      (fib (- n 1))
      (fib (- n 2))))))

This will help the compiler by telling that the n-argument is always an integer. You can also add more information to the declaration:

(defun fib (n)
(declare (integer n)
         (optimize (safety 0)
                   (speed 3)))
(cond
  ((or (eql n 0) (eql n 1)) n)
  (t (+
      (fib (- n 1))
      (fib (- n 2))))))

Now we're looking at some directives about how the compiler prioritize between safety and speed. You can also add directives for how much debug information should be retained or if the compiler should improve speed or size. All of this is interesting, but if I compile it with SBCL I'll get a few warnings. I've specified I want a high level of speed and low safety, but there are many optimizations that SBCL still can't do, so it warns about them. In most cases it's because there is no way to see if the result of the fib-operations return numbers, floats or rationals. If fib is seen as a bottleneck, the way to fix this is to add declarations inline the code in the style of this: (the numeric (- n 1)) and so on. This will allow the compiler to generate the best code possible.

Now, these kinds of changes are quite intrusive, and they aren't really something you want all over your code base. That's why you can do these declarations selectively, at only the places where it makes sense from a performance perspective to do it. By doing it correctly, Common Lisp code can be compiled to be incredibly efficient and fast, but very clean since in most cases you don't add the type declarations at all.

This is also why Common Lisp is very good for rapid prototyping. You can get something working really quickly, but you can also change the code to be efficient later on with quite small changes.

I guess you all wonder what this has got to do with Ruby. Or maybe you don't. Anyway - I want this in Ruby, or something equivalent to it. Not necessarily the exactly same thing, but something which in a standard way can add type declarations and also other things that can be interesting to know from a compiler perspective. It needs to be a keyword with specific syntax so the information is available before runtime. It should probably be used for the encoding declarations too, so it should be possible to use either at top level, or within class declarations , or method definitions. What do I want to be able to do? Well, type declarations is the first one. The second is compiler directives that can help improve code more than is possible right now. A typical example could look like this, maybe:

declare encoding: utf-8

def test_one(first, second, *rest)
 declare type: [Fixnum first, Enumerable second, Array rest]
 declare return: Fixnum
 declare compiler: [no-bindings, no-eval, no-closures]

 puts "hello"
 return 1+1
end

This code includes several things that would be very useful to know and would allow compilers like JRuby, XRuby, YARV, Rubinius and IronRuby to produce much better code. If we know that the arguments should always be specific types we can declare this and hopefully get better results. The return value is also usually the same type and declaring this can make code that uses this method more efficient. Finally, the compiler declarations will help with some of the pain points for currently compiling things efficiently. If no bindings, or evals or closures are used, the code generated will be much better.

This kind of information would be very useful not only for the compiler but also for tool support. If you know something should always be a specific type, you can add that as a declaration and things will automatically function better.

I know that this is kind of un-Ruby like, but I really believe there is great value to be had by adding this kind of declarations.

JavaScript 2

After all discussions about the NBL and all surrounding issues, I realized I haven't actually looked at what JavaScript 2/ECMAScript 4 will contain. I decided to do some research. What I found was mostly very old (2 years or so), but very enticing. If only half of it comes true, JS2 will be a power house. Of course, the C inspired JS syntax is still kind of repugnant, and it's hard to see any kind of general purpose macro facility working on it. Pattern matching is the only reasonable way of getting macros in there, me thinks, and that just doesn't pack the same power.

But still, there are seriously nice things there:

• Classes (the classic kind), packages and namespaces
• Destructuring
• Generators and iterators
• A real numeric tower
• Optional static typing

The end result is that JS2 will look much more like Java, but pack greater power in many ways. I wouldn't say that I agree about JS2 being the NBL, but we're still talking some nice innovation here.

ThoughtWorks Immersion

I've just come back from Bangalore, India where I spent two weeks with intense learning, much socializing and incredible amounts of fun. In short, I've attended ThoughtWorks Immersion. I found it to be a singular experience, and something that will be immensely helpful during my career at ThoughtWorks.

So what is Immersion? Basically, it's two weeks of learning that all ThoughtWorkers go through. The aim is not really to teach technical concepts or specific ways of working, but more to establish a common vocabulary, get everyone to understand the history of ThoughtWorks, and also give insight into all parts of the organization. How everything works and how we do things. A large part also is about what makes ThoughtWorks different from other companies, both in the way we do things but also the why of it all. The values TWers should share and what makes TW a unique place to work.

I feel I've learned incredibly much. The two weeks away from regular work was hard but definitely worth it. I wish all companies had something like this - but I guess that this is one of the ways that make TW a very different place.

The learning side was important, but the social aspect probably even more so. I now have 13 new friends within ThoughtWorks, spread all over the world. We had a good time together. Also, Bill Kimmel and Naresh Jain turned out to be outstanding teachers and very nice people to boot.

Of course, the stay in Bangalore got even more productive when Roy Singham, Chad Wathington, Cyndi Mitchell and a few other people arrived there. I spent some time with them, planning and scheming.

Meeting Håkan Råberg and seeing the cool stuff he's working on (still secret) was also very nice.

All in all, two weeks well spent.

Upcoming

Next week I'll be in Berlin for RailsConf EU. I'll be speaking about JRuby at ThoughtWorks, and hopefully I'll meet lots of you there.

ThoughtWorks is actually massively involved in this RailsConf, and I'm hoping for the same kind of energy I observed at RailsConf in Portland.

See you next week!