As Yet Unclassified

The five-line sinatra app on http://www.sinatrarb.com/ is pretty damn impressive:

require 'rubygems'
require 'sinatra'
get '/hi' do
  "Hello World!"
end

I can do four lines better than that, though:

require 'sinatra'

So what does that get you?

batkin:cholla ben$ ruby -rubygems cholla.rb
== Sinatra/0.9.0.4 has taken the stage on 4567 for development with backup from Thin
>> Thin web server (v1.0.0 codename That's What She Said)
>> Maximum connections set to 1024
>> Listening on 0.0.0.0:4567, CTRL+C to stop
127.0.0.1 - - [03/May/2009 10:13:46] "GET /index.html HTTP/1.1" 200 7 0.0019

A basic http file server, perfect for working with plain html, javascript, and CSS! Just create a public/ directory alongside the one-line sinatra app, and have at it! If you create an index.html file in public/, it will be served up when you go to http://localhost:4567/. Try it!

Once you decide to add some server-side code, you can simply go in to the sinatra app and add it.

I just watched Corey Haines’ lightning talk from this year’s acts_as_conference:

He makes a lot of really good points in a short amount of time. One of the things he says is that if we have to look at documentation for a technique, we’re unlikely to use that technique when we’re in a time crunch. I think this is a very good point. Another time when I might not use the documentation is when I’m just dabbling.

To learn things, he suggests doing arbitrary tasks repetitively to get them engrained into our minds.

I spent a number of hours doing arbitrary tasks with vim, and I’ve gotten pretty good at using vim IMHO. I wish I could say I was as good at jQuery, but I haven’t got it down as well despite doing real projects in it. I think perhaps it’s best that I pick an arbitrary task, or at least do a real, but small, task repetitively, or keep trying to improve it, until I start to really get the hang of it.

On a side note, Corey Haines’ has quit working a regular job and started traveling around and pair programming with people in exchange for room and board. He calls himself a Software Journeyman. It will be interesting to hear what he learns from the experience. I hope his journey takes him to Arizona at some point!

When installing Merb on my laptop, which runs Ubuntu Linux, I ran into a compiler error with hpricot, one of Merb’s dependencies. Before bothering to see what might be causing it, I checked to see if there was a precompiled apt-get package available. There was! I installed it and tried installing Merb again.

It still tried to install hpricot, however, and when I said to skip it, it said it could not install Merb because it was missing hpricot. I could have used force, or “pretty please”, but I wanted to instead tell the packaging system that I have hpricot installed.

I seem to remember a UNIX packaging system having an inject command — which tells the packaging system a program is already installed. I may have got the terminology wrong. I searched for such a command for rubygems but couldn’t find one. I did, however, find another way to convince rubygems that I already had hpricot.

I decided to do some digging in the gems directory. To find the gems directory, I typed:

ben@magicthise:~$ gem environment
RubyGems Environment:
  - VERSION: 0.9.4 (0.9.4)
  - INSTALLATION DIRECTORY: /var/lib/gems/1.8
  - GEM PATH:
     - /var/lib/gems/1.8
  - REMOTE SOURCES:
     - http://gems.rubyforge.org
ben@magicthise:~$ cd /var/lib/gems/1.8/
ben@magicthise:/var/lib/gems/1.8$ ls
bin  cache  doc  gems  source_cache  specifications
ben@magicthise:/var/lib/gems/1.8$ cd specifications/
ben@magicthise:/var/lib/gems/1.8/specifications$ ls
abstract-1.0.0.gemspec          merb-cache-0.9.2.gemspec
actionmailer-2.0.2.gemspec      merb-core-0.9.2.gemspec
...
ben@magicthise:/var/lib/gems/1.8/specifications$

I took a look at the gemspec files and found that they contained the name and version of the library. I copied the smallest of the files to hpricot-0.6.gemspec and used the gemspec documentation to find out which parameters are required. I wound up with the following in /var/lib/gems/1.8/specifications/hpricot-1.6.rb.

Gem::Specification.new do |s|
  s.name = %q{hpricot}
  s.version = "0.6"
end

I tried running:

ben@magicthise:~$ gem install merb --include-dependencies

And it worked!

It might not be everything that’s needed to get it working — but now I at least know how to inject a package.

I just read an article calling for a way to get an AST for Ruby code from within Ruby. I think it’s a great idea, and I think static analysis, code manipulation/refactoring are great reasons to support such a thing. Another consequence would be macros, which are a more controversial feature. The only downside I can think of is that it could be misused, and to leave out a feature for that reason would go against the Ruby philosophy, in my opinion. One of the regulars at the Phoenix Ruby Users’ Group argued against using a dumbed-down “teaching language”, saying that when you suggest using a language you don’t want to use yourself, you’re talking down to the learner. I agree. I think the best way to keep people from misusing features is not to remove the features, but to educate them. People in the Ruby community have always done a good job of making sure there’s lots of good example code out there, and giving constructive criticism when someone posts a bad example.

While the reasons in the article are enough, I can think of another good reason for having AST support — having the ability to constrain code to a certain set of features. There would be two different uses for this:

• Running code from an untrusted source – This could include web template designers, or even users. Ning is an example of a site that lets users run their own code — but there is a huge overhead to facilitate this and to sandbox everything. If it could be verified that code doesn’t do anything dangerous, I think a new type of Web app plug-ins would emerge. Instead of having to set up an app on a separate site and use REST or SOAP to communicate, people could just throw together a little script in a domain-specific language. One idea I have for this sort of technology would be a Flickr for html and image generators (like ajaxload.info).
• Enforcing decoupling – When managing a large software project, I think it would nice to specify which classes do what, and have it enforced. Maybe there is some class that’s supposed to be all about math, but that goes in an application that gives output to users. To keep math programmers from putting presentation logic in mathematical code, you could constrain them to a DSL that doesn’t have strings. Or, you could keep template programmers from doing networking code. The check could be done at runtime, or commit time, with plug-ins to the version control system.

There is a Perl library that parses Perl, but it would be nice to have one for Ruby that’s written in C and optimized for speed, and that with certainty matches up to what the interpreter understands.

I think that once an AST implementation was built, something like RSpec could be created which does compile-time or commit-time analysis. That would be cool.