Oleg Andreev

We assume you had Leopard with standard Ruby shipped with OS, tons of macports and rubygems already installed. Then you install Snow Leopard on top of it (not clean install).

The problem is that standard 10.6 dynamic libraries all went 64 bit and could not be linked with 32 bit code. This could be fixed by rebuilding/reinstalling all the macports and rubygems.

1. Install the latest Xcode shipped with Snow Leopard.

2. “port” command will fail with a message about incompatible Tcl architecture. The proper version of macport is 1.8 which is not released yet. You can obtain it from SVN trunk and built it by hand (./configure && make && sudo make install). I have also added trunk version of ports to sources.conf (see the link above for instructions) to be sure that I have the latest SL-compatible ports in the list. Maybe this is was wrong assumption, but it worked for me just fine.

3. Remove all ports:
$ sudo port -f uninstall installed

4. Update rubygems to 1.3.1 at least (please google for instructions).

5. Remove vendor gems (gem uninstall refuses to remove them and fails to do batch remove):

$ gem list | cut -d" " -f1 > installed_gems
$ sudo mv /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8 /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8.bak
$ sudo mkdir /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8

Note: installed_gems file contains a list of all installed gems so that you can cat and xarg it for installing all gems back.

6. Uninstall all gems

$ sudo gem list | cut -d" " -f1 | xargs sudo gem uninstall -aIx

7. Make the rubygems use 64 bit architecture.

$ cat installed_gems | xargs sudo env ARCHFLAGS="-Os -arch x86_64 -fno-common" gem install --no-ri --no-rdoc

Note: it is NOT i686 (as I thought it should be), it is x86_64 instead.

Here are convenient aliases for “sudo gem install” for both architectures:

alias sgi32="sudo env ARCHFLAGS=\"-Os -arch i386 -fno-common\" gem install --no-ri --no-rdoc"
alias sgi64="sudo env ARCHFLAGS=\"-Os -arch x86_64 -fno-common\" gem install --no-ri --no-rdoc"

You may also put alias sgi="sgi64" in your .bash_login on snow leopard.

Now we all can proceed doing productive work. \o/

References:
1. http://www.nabble.com/-MacPorts—19446:-openssl-fails-to-compile-on-x86_64-td23247203.html
2. http://jaredonline.posterous.com/got-mysql-to-work-with-rails-in-mac-os-106-sn
3. http://cho.hapgoods.com/wordpress/?p=158

Object interface is a set of messages with defined behavior the object should respond to.

In statically typed languages, interface is required by type declaration. In dynamically typed languages this is done by telling object of unknown type to cast itself to the desired type.

# User's code expects object responding to #to_page
# when casted to page, we expect proper #render and #size behavior
class SomeController
  def process(object)
    page = object.to_page
    page.render
    page.size
  end
end


# 1. Page class with #to_page interface returning self
class Page
  def to_page
    self # return self since it is already a page
  end

  # page public api

  def render 
  end

  def size
  end
end

# 2. Non-page class with #to_page interface
class AtomicBomb
  def to_page
    # return a relevant article
    Page.wikipedia_article("Nuclear weapon")
  end
end

# 3. Class without #to_page, but with #render method
# fails with "object does not respond to #to_page" exception
# and does not cause undesirable side effects
class Foo
  def render
    # very specific nasty rendering method
  end
end

# 4. Class without #render
# fails with "object does not respond to #to_page" exception 
# rather than with less descriptive "object does not respond to #render"
class Baz
end

This technique minimizes duck typing collisions by reducing the number of exposed methods to a single “to_{unique_type_name}” method. It also protects you from inventing obtrusive method names with type prefixes such as “page_render” or “page_size_in_characters” (see example above).

The rule of thumb:

1. When API consists of more than one method, introduce #to_my_type method

2. Whenever you receive an object from an unknown source (e.g. defined in a different file), use explicit type casting with #to_some_type method.

Note: never ever make others ask about the kind of an object using #respond_to?. This method should be used for legacy code and indicates possible duck typing issues.

Also, #is_a?(SomeAbstractInterfaceModule) is considered badly designed compared to #to_* methods.

Parser.js
JSONGrammar.js

The parser enables you to write BNF-like rules directly in JavaScript without need to compile the file (like with Ragel, YACC, Bison, ANTLR etc.)

The grammar is a JS function with 11 arguments (9 rules and 3 hooks). Each rule gets two arguments: text (string) and state (arbitrary value) and returns a tuple of new text and new state (or null if rule was not matched). Parser walks character by character from left to right. text is always a tail of the initial text. Generally, text is empty string when parser finishes.

All(rule1, rule2, …) — a sequence of rules. Example: All(Char(“[”), list, Char(“]”)) defines a JS array.

Any(rule1, rule2, …) — “OR” rule for any number of rules. Example: JSONValue = Any(StringRule, ObjectRule, ArrayRule, …)

Char(alphabet) — character matching rule. Example: digit = Char(“0123456789”)

NotChar(alphabet) — inverse of Char(). Any character — NotChar(“”).

Optional(rule) — tries to match rule and skips it if not matched. Example: optSpace = Optional(Char(“ \t\r\n”))

EOF — matches the end of the text. Fails if text != “”.

Terminator — terminates parser. That is, always returns empty text.

Y — Y-combinator for defining recursive rules. Example: X = Y(function(x) { return abc(x) } ), where x is equal to X. Google for more info on Y-combinator.

Hooks enable you to actually build some structures using your grammars. Every hook returns a new state value to use in further rules. You should avoid mutable state values because some rules may be thrown away if not matched later (remember: this is a recursive parser!). For example, use array.concat([value]) instead of array.push(value).

Capture(rule, function(buffer, state1){ return state2 }) — captures raw string buffer to store in the state2.

Before(rule, function(state1){ return state2 }) — creates a new state for the rule (e.g. creates empty array for array syntax).

After(rule, function(beforeState, afterState){ return newState }) — creates a new state after successful match. You can put nested values to the container if beforeState is a container before rule parsing, afterState is a nested value (after rule match) and newState is a new container with this value.

See usage examples in JSONGrammar.js

See the parser source code in Parser.js

Implementation is created under time and knowledge constraints. Therefore, it is full of bugs, and it becomes obsolete as soon as our knowledge evolves. What is important in technology: the idea and context behind each decision.

There’s no “srand” function in AS3. That is you cannot seed random number generator.

And when you get the very same results each time swf is loaded you find this:

However, if you need true randomness in an event-driven application, you can do this:

setInterval(Math.random, 10)

Flash Player will run Math.random() in background producing different random values at different points of time.