Ruby Weekly News 6th - 12th June 2005

T

Tim Sutherland

http://www.rubyweeklynews.org/20050612.html


Ruby Weekly News 6th - 12th June 2005
-------------------------------------

Ruby Weekly News is a summary of the week's activity on the ruby-talk
mailing list / the comp.lang.ruby newsgroup, brought to you by
Tim Sutherland.

Articles and Announcements
--------------------------

* Ajax on Rails
---------------

The third Curt Hibbs ONLamp.com article covering the
Ruby on Rails web application framework.

This time it's about Rails' Ajax support, which makes it
super-easy to create web sites that use asynchronous
Javascript calls.

It was also posted to Slashdot.

Nearby, Curt posted the latest version of his Rails presentation, see
the thread [My Rails presentation is available for download].

"It includes a video that goes through the entire development process
for the cookbook application in part 1 of Rolling with Ruby on Rails".

* RubyStuff: The Ruby Shop for Ruby Programmers
-----------------------------------------------

James Britt announced the "formal grand opening" of RubyStuff.com.

"In an effort to help fund ruby-doc.org and rubyxml.com, I assembled a
variety of designs and opened up multiple shops on CafePress to hawk
apparel, clocks, mugs, mouse pads, assorted sundries."

* LinuxJournal awards are open for voting...
--------------------------------------------

Tom Copeland noticed that Ruby is in the programming language category
of the Linux Journal Readers' Choice Awards 2005.

The first round of voting has begun and is open to anyone with an
email address.

* http://sciruby.codeforpeople.com/
-----------------------------------

Ara.T.Howard announced the Scientific Ruby Wiki.
It is "a place for all things scientific and ruby. come join us!"

It includes a [WeeklySpotlight] page, which has something new every
week.

Quote of the Week
-----------------

Daniel Berger on RubyStuff.com shirt designs:
|
| I'm still waiting for my "Ruby programmers do it with class" t-shirt.
|

Link of the Week
----------------

Lambda the Ultimate - The Programming Languages Weblog.
http://lambda-the-ultimate.org/

Lots of interesting posts, if you're into that programming language
junk ;-)

Threads
-------

Interesting threads included:

finding Hash subsets based on key value
---------------------------------------

ee began
| Is there a simple way of searching the keys of a Hash to find a
| subset. I have a set of keys with two values indicating group and
| sub-group", for example "group_1_item_1", "group_1_item_2",
| "group_2_item_2".

"I'd like to divide them into groups, but without having to loop through
the entire collection and having to test each key".

Martin DeMello said that it isn't possible to solve this problem without
testing each key, but gave a single line using Enumerable#partition that
otherwise met the criteria.

| Enumerable#partition divides your collection into two parts, based on
| whether the block returns true or false, so it doesn't scale to more
| than two subsets, but for your example it should work nicely."

Robert Klemme thought that perhaps we should have a
Enumerable#general_partition method that partitions into "several buckets
and not just two." He gave a sample implementation.

James Edward Gray II popped in with the best answer: The standard
Set#classify. It can be used as follows,

----
require 'set'

items = Set[
'group_1_item_1',
'group_2_item_2',
'group_1_item_2',
'group_1_item_4',
'group_2_item_3',
]

groups = items.classify { |name|
name[/^group_\d+/]
}

p(groups)
# { "group_2" => #<Set: {"group_2_item_2", "group_2_item_3"}>,
# "group_1" => #<Set: {"group_1_item_1", "group_1_item_2",
# "group_1_item_4"}> }
----

Set#classify groups items by whatever the block returns for them - in this
case the prefix of each item.

python/ruby benchmark
---------------------

</script> (yes, that was the name) took a look at
`The Computer Language Shootout Benchmarks' page comparing the
performance of Ruby and Python in various micro-benchmarks.

To his disappointment, Python performed better.
"So what I'm asking for is a link to some ruby-specific optimisation tips."

Various people commented that such benchmarks do not mean that Ruby is
slow in real-life programs.

Austin Ziegler:
| At any rate, I consider the Alioth shootout to be harmful to all
| languages involved. There is no useful value provided by it,
| especially as it does not permit language-appropriate modifications
| to the algorithms in use.

Austin also called the benchmarks "bogus", and some other, less polite,
things.

Phil Tomson said that this was blaming the messenger.
| If we keep telling ourselves that Ruby is `fast enough' for our
| application (and it may well be) are we going to be sitting still
| while other languages improve performance?

The (sometimes hostile) thread continued for over 60 posts.

framework of Ruby/Tk + VNC
--------------------------

Hidetoshi NAGAI announced that he is working on a framework utilising
Ruby/Tk and VNC. "Its purpose is to put GUI applications of Ruby/Tk on
internet view", running "on a safe (safe-Tk) based slave interpreter".

VNC connects to a Tk canvas, with no external window manager. "In the
future, it may be expected that Ruby/Tk has RFB server functions and no
VNC server is required for this purpose." (RFB = Remote FrameBuffer.)

He compared this scheme with using the tclplugin web browser plugin to run
the Tk client on the user's computer.

FXRuby 1.2 with Fox 1.4?
------------------------

Tom Nakamura knew that FXRuby 1.2 was designed to work with Fox 1.2, but
wondered whether it would work with Fox 1.4, since "There's no FXRuby 1.4
yet".

Lothar Scholz said that it wouldn't work, since Fox 1.4 changes the names
of many methods in an effort to make them more consistent.

how to extract url's from html source of google search result
-------------------------------------------------------------

Sujeet Kumar was able to retrieve HTML from a website using Ruby, but was
stuck at the next point: how to extract URLs out of the result.

Marcel Molina Jr. suggested the URI.extract method from the `uri' library.

----
require 'uri'
URI.extract('My favorite site is http://google.com')
# => ["http://google.com"]
----

| An optional second argument can limit the schemes that it will match
| against and return" so, for example, you can tell it only to retrieve
| `http' links and not `mailto' etc.

Alexey Verkhovsky thought that URI.extract was potentially troublesome
because it is implemented using a regular expression - "it can produce
false positives (finding things that look like URIs, but aren't)".

| If you are sure that the page is a well-formed XHTML (I'm not sure if
| that's the case or not with Google), you might instead parse it with
| REXML, and use XPath to retrieve href attributes of all <a>..</a>
| elements, selecting only those that start with "http://" (there may
| also be mailto:, ftp:, JavaScript calls etc).

As an entirely different solution, Eric Hodel asked why the original
poster didn't juse use the Google API (web-service).

text to images using RMagick
----------------------------

Nick Hayworth wanted to convert a string to an image using RMagick,
automatically wrapping at a certain number of pixels.

He already had this working using the convert utility that comes with
ImageMagick.

----
convert -size 200x -font Tahoma -pointsize 20 caption:"My very long caption
which should wrap at 200 pixels" output.gif
----

Timothy Hunter released a new version of RMagick (version 1.8.2) and
announced that it was indeed possible ;-)

The following code will do it:

----
require 'RMagick'
include Magick

img = Image.read("caption:My very long caption which should wrap at 200
pixels") do

self.size = "200x"
self.pointsize = 20
self.font = "Tahoma"
end

img[0].display
----

Persistence of Ruby sessions/programs
-------------------------------------

Renzo Orsini:
| I know there are several ways of saving ruby objects on
| files, but there is a simple way of saving ALL the state of a Ruby
| program execution (or an irb work session) and then reload it in
| another execution (or session)?"

gabriele renzi said that a "hackish" solution would be to store the source
you entered in irb and eval it back later. "Saving the state of the
program would be hard since you can't serialize closures, singletons and
continuations".

Renzo Orsini noted that he would be "happy just to save classes, objects
and global variables that I have defined, or a subset of them, but it
seems to me that with Marshal.dump I cannot even save a class".

blocks, scope/context confusion
-------------------------------

Corey, learning Ruby from PickAxe2, was having trouble in the section on
blocks.

"What's the difference between the two methods below?"

----
def meth1
yield
end

def meth2(&b)
b.call
end
----

He also asked why "meth { return 99 }" throws a LocalJumpError.

To the last question, Matz said the error was because even the bare
return 99 at the top-level causes an exception. He suggesting Corey try

----
def foo
meth1 { return 99 }
end
p foo
----

For the other questions, Gary Wright said that yield and b.call were
equivalent. "The first example is syntactic sugar for the second example."
He noted an implementation difference in them; the former is slightly more
efficient.

Devin Mullins gave a link to an article on "closures" (another name for
blocks).

Chess Variants (I) (#35)
------------------------

James Edward Gray II posted this week's Ruby Quiz. It is reminiscent of
the idea behind the 2005 ICFP Functional Programming Contest.

| One of the greatest challenges in programming is modular design.
| Building code that adapts well to change is a Holy Grail quest for
| most of us. This two-part Ruby Quiz is designed to put your ability
| to predict the future to the test.

The first part of the problem is to build an engine for two player chess.

There is no need to create AI or other features, "just a board and piece
interface players can use for games. The game should prevent illegal
moves, make sure the right player moves at the right time, declare a
winner when a game ends, etc."

"Next week, in part two of this quiz, I will provide a list of chess
variants you are expected to modify your program to support."

(Aha! The twist.)

get username of file owner?
---------------------------

John Fry wanted to find the username of whoever owned a particular file.
He could get the uid with File.stat("testfile").uid, but how might he
retrieve a username such as "smith" instead?

Fredrik Fornwall showed how to use the `etc' library to convert a uid to a
username:

----
require 'etc'
uid = File.stat('testfile').uid
puts 'Owner name: ', Etc.getpwuid(uid).name
----

duck-typing allows deeper polymorphism
--------------------------------------

Eric Mahurin posted the advantages he sees of duck-typing over
"conventional polymorphism".

See also the [making a duck thread] from earlier in the week.

problem matching accented chars on OS X
---------------------------------------

Alex Fenton wrote: "I'm finding words within strings in Western European
languages, so I need to account for accented characters, such as ê (e
circumflex) and à (a grave)."

He can match them in reguar expressions by including "\xC0" and so on in
the expression - the hex representation of characters in the iso-8859-1
encoding.

This works on Windows, but when he tries to run the same code on Mac OS X,
he gets an error about "mismatch multibyte code length in char-class
range".

Axel (now that's confusing!) replied, saying that a regular expression
such as /abc/U can be used to specify that the expression is encoded in
UTF-8.

Other character sets, such as EUC and SJIS are supported in a similar way.

Axel later added that the Oniguruma regular expression library supports
more encodings. It is the standard engine in Ruby 1.9.

Rails on Altix ia64
-------------------

Adam P. Jenkins was getting "[BUG] Segmentation fault" messages when
running Ruby on an Altix IA64.

Tanaka Akira posted a patch which solved Adam's problem, but noted that
issues on IA64 still exist.
(Particularly around the way the GC interacts with registers.)

Getting a method object directly from a module
----------------------------------------------

Daniel Berger asked how he could extract a method from a module.

----
module Foo
def my_method
end
end

method = Foo.method:)my_method)
=> NameError: undefined method `my_method' for class `Module'
----

Matz:
----
Foo.instance_method:)my_method).bind(obj).call
----

A little Quiz
-------------

Dominik Bathon wrote some code that uses method_missing for an unspecified
purpose, and challenged the group to figure out what it does.

Later ... "As James Britt already figured out, it lets you call one method
on all elements of an Array. If no block is given this works like
collect."

| Instead of
|
| [-1, -2, -3].collect { |x| x.abs }
| => [1, 2, 3]
|
| you can just write
|
| [-1, -2, -3].abs
| => [1, 2, 3]
|
| Since #abs is not part of the Array interface, method_missing is
| triggered. But it does more than collect, it even works on nested
| Arrays:
|
| [[-1,-2],[-3,4],-2,5].abs
| => [[1, 2], [3, 4], 2, 5]

Accessing SVN through Ruby/DL
-----------------------------

Jim Morris was wandering through an old thread which discussed the merits
of binding Subversion through SWIG or Ruby/DL.

"I cobbled together the following to see how hard it would be to do this
in DL."

"I hope this can be added to the samples, as it involves callbacks,
structures and pointer types."

Takaaki Tateishi thanked him, and added the sample program to the
DLCookbook project.

Ruby/LDAP on Windows
--------------------

gregarican was having trouble building Ruby/LDAP on Windows.

extconf.rb was complaining that it couldn't find `ldap.h', `lber.h' or
`ldap_ssl.h'.

The headers were under `c:\openldap-2.2.26', and gregarican had tried
passing in arguments such as --with-ldap-dir="c:\\openldap-2.2.26".

There weren't yet any replies.

Perhaps using '-with-ldap-incdir' to point directly to the header
directory may help?

Array#nitems and Object#nil?
----------------------------

Matz re-discovered a March post from Bertram Scharpf that proposed adding
a block to Array#nitems.

"Today, I happened to re-discover this mail, and found it reasonable.
Array#nitems will be able to take a block to count items specified by the
block (CVS HEAD)."

Could Ruby-doc be better?-Proposal for a better system
------------------------------------------------------

Andrew Thompson thought that ruby-doc.org could use some inspiration from
the PHP manual.

| My basic plan is to have a php style manual
| http://www.php.net/manual/en/ generated from the rdoc comments,
| with the ability to have the documentation maintained in a wiki
| based fashion, and have user comments along the lines of the PHP
| manual. This way we lower the barrier to writing documentation,
| allow users to comment with code samples or additional info, and
| hopefully increase and improve the amount of documentation ruby has.

Can't see the ground `cause my chest is so puffed out!
------------------------------------------------------

Timothy Hunter:

| Following the Rails Day links from /. I was immeasureably pleased to
| discover that at least 2 Rails Day qualifiers
| (http://railsday.com/svn/qualifiers) used RMagick!

You might guess that Timothy is the creator of RMagick, the Ruby bindings
for the ImageMagick and GraphicsMagick image manipulation libraries.

Gambit Codefest Postmortem
--------------------------

James Edward Gray II,

| We've just completed nine solid days of development on Gambit. Now
| that's a "Codefest" alright! I thought I would share a little with the
| curious about how I think it went...
|
| Greg Brown flew out to my home in Oklahoma so we could work on Gambit.
| It was nice to finally meet face-to-face. We've actually programmed
| together on many projects these last couple of years, but this was the
| first time we didn't do it over the Internet. We're both grateful to the
| wonderful people at Ruby Central for giving us that opportunity.

....

| Which brings us to what we built. Some of you have expressed interest in
| Gambit and I'm sure you would like to hear how it came out. The short
| story is, very good. We met and even exceeded our expectations in many
| areas.
|
| The longer story: We've built a very hand model layer for common game
| elements like Boards, Cards, and Dice. This is probably our most
| polished work and has been a real asset to our internal development
| already.

.... with lots and lots of unit tests.

New Releases
------------

* constraint 0.1-ensure that object always satisfy a specified set of
constraints
---------------------------------------------------------------------

Thomas announced the "first draft" of `constraint', a library that
assists in adding constraints to objects. In particular, it is used to
implement typed collections.

* RDoc Dashboard Widget
-----------------------

David Felstead created an RDoc Dashboard widget for Mac OS X Tiger. It
reads any RDoc repository and "lets you check your documentation
without having to open a Safari/Firefox window."

"I'm also working on an IRB widget which should be done shortly, if
anyone's interested."

Gavin Kistner: "Hot damn, that's awesome! Just what I was looking for
and thinking of when Tiger came out."

* ruby2c 1.0.0 beta 3
---------------------

Ryan Davis released the third beta of ruby2c 1.0.0.

| Ruby2C provides a pipeline of SexpProcessor classes to work with
| ParseTree output. Processors included:
|
| Rewriter - massages the sexp into a more consistent form.
| TypeChecker - type inferencer for the above sexps.
| RubyToC - converts a ruby (subset) sexp to C.

* Tiddy 0.0.4
-------------

Dr Balwinder S Dheeman updated Tiddy, a program for re-formatting Ruby
source code. (And Ada, C, C++, Java, C#, Perl, ...)

See also Tiddy 0.0.3-pre3 is released.

* FireRuby 0.3.1
----------------

Peter Wood enhanced the Connection class in FireRuby 0.3.1, the
bindings to the Firebird RDBMS.

It now rolls back outstanding transactions whenever the close method
is called.

* Ruby Month 0.1.0
------------------

Francis Hwang, from "out of murky depths of the Lafcadio codebase",
released a utility library called Ruby Month.

It is used, unsurprisingly, to make it easier to manipulate months.

* Ruby/Odeum 0.4: ResultSets, KirbyBase Demo
--------------------------------------------

Zed A. Shaw announced Ruby/Odeum 0.4, a binding to the QDBM Odeum
full-text search engine.

This release is 15-20% faster than the last, and includes a KirbyBase
wrapper that "indexes records on the fly and allows you to do full
text search for them".

--
 

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