Show me the code

2010-09-27T10:37:45+02:00

After reading and agreeing with Show me the code some time ago, I thought about how to integrate source code examples on the XP Framework website. While lots of blog postings here contain sourcecode, this is not prominent enough - so I set up a new site dedicated to this purpose: The XP Code galleries. Enjoy

Array dereferencing

2010-09-22T08:10:13+02:00

While array dereferencing was added to the PHP runtime's so-far unreleased SVN trunk a while ago, this feature isn't going to be backported to older PHP versions, which the XP-Framework will continue to support for quite a while. We've thus added a core functionality, this(), to make indexer access possible:

  $a= $class->getMethods()[0];         // Supported in PHP as of 2011*
  $a= this($class->getMethods(), 0);   // The XP-Framework way

* Educated guess, there is no communicated release date for PHP "next"

Y2K38

2010-08-25T10:28:28+02:00

In a recent Sitepoint article, the author talks about problems with PHP's strtotime() function, which can be basically summed up to this:

  $ xp -e 'Console::writeLine(date("l d F Y H:i", strtotime("2040-02-01")));'
  Thursday 01 January 1970 01:00

The problem is the internal representation of dates, which will overflow and thus cause strtotime() to yield an incorrect value.

The XP Framework's util.Date class, being based on PHP's DateTime class, will not exhibit this problem, regardless of whether the system is 32-bit or 64-bit.

  $d= new Date('2040-02-01'); 
  Console::writeLine($d->toString('l d F Y H:i'));  // Wednesday 01 February 2040 00:00

See also and - with a humouristic take:

Generics in C#, Java, and C++

2009-11-14T10:55:52+01:00

In this interview from quite a while ago Bruce Eckel and Bill Venners talk with Anders Hejlsberg about generics implementations in C# and Java - the differences in their implementations, type erasure vs. runtime instantiation, reflection and how they compare to C++'s template mechanism. This has inspired us to come up with RFC #0193 - and moving our generics implementation closer to the one in the CLR.

Type hinting discussion and contracts

2009-07-12T18:48:13+02:00

In the recently ongoing type-hints discussion on the PHP internals mailinglist (see also the PHP Wiki), an interesting proposal was made. It suggests using functions to verify argument types instead of introducing a type checking mechanism which is not strict enough for some, not flexible enough for others and too magic for yet another group.

  function array_of_numeric($x) {
    foreach ($x as $val) {
      if (!is_numeric($val)) return FALSE;
    }
    return TRUE;
  }
  
  class Arrays {
    public static function sum(array_of_numeric $a) {
      return array_sum($a);
    }
  }

PHP-Arrays: Maps and lists

2009-04-05T12:30:39+02:00

In the PHP world, arrays are maps are lists:

  $a= array(1, 2, 3);                // #1: A list
  $b= array('key' => 'value', ...);  // #2: A map
  $c= array(1, 2, 'a' => 'b');       // #3: Mix of both

Now this is (almost) perfect as long as you stay inside the PHP world; the only thing you have to know is when to be able to use array functions operating on "associative arrays" (like asort) instead of "numeric arrays" (sort), which is usually achieved by a bit of discipline. This is where a slight problem even inside the PHP world (and that's why it's only almost perfect) starts showing: There is no easy way to keep the both apart.

Casting an object array to a string array

2008-07-19T21:15:28+02:00

While testing the new EASC server and client implementations we're currently working on, we asked ourselves how to cast an object array to, for example, a string array.

The following is an array of objects consisting solely of strings:

  Object[] strings= new Object[] { "Hello", "World" };

The first thing we tried was to cast it via (String[])strings. This is legal sourcecode but will raise a java.lang.ClassCastException in Java, and a System.InvalidCastException in C#, both at runtime.

Exceptions in Java

2008-06-25T10:57:27+02:00

Found this nice article on exceptions in Java - from a historic overview of Oak, on checked and unchecked exceptions, and asynchronous exceptions it explains nicely (and with code examples) what the Java exception mechanism is about. What I like most are the best practices section, which applies not only to Java:

Don't Write Own Exceptions
Write Useful Exceptions
Throw exceptions early
Catch exceptions late
Document exceptions
Unit Test Exceptions

Frank Kleine on Namespaces

2007-11-11T21:33:00+01:00

On a short note: In Gathering practical experience with namespaces, Frank describes his first impressions of PHP 5.3 with namespaces:

Oh boy. You should never even think about porting your application completely to namespaces if you do not have enough unit tests!

Reminds me of the rule of thumb that one never has enough unittests

PHP6 Namespaces patch backported

2007-07-21T15:23:12+02:00

Beginning of this month, Dmitry Stogov from Zend published a patch implementing namespaces in PHP6.

To be able to begin playing around with it without adding further points of possible failures for our XP unittests with new PHP6 (e.g., unicode-related breakage), I started and after a day's work succeeded in backporting the patch to current CVS HEAD, that is, PHP 5.2.4-dev.

Scala

2007-04-07T11:43:12+02:00

Found this while surfing the web for Java 7 ideas:

Scala is a general purpose programming language designed to express common programming patterns in a concise, elegant, and type-safe way. It smoothly integrates features of object-oriented and functional languages. It is also fully interoperable with Java.

I can't believe it's not XML!

2007-03-31T16:53:54+02:00

Really enjoyed reading a weblog entry I found while surfing around for JSON-related stuff.

There seem to be a lot of XML folks who can't understand JSON - yes, Dave, it's not even XML. I have a theory on why that is, but to explain it I need to go into a couple other things first.

Static initializers

2007-03-29T10:06:05+02:00

Nice to see other folks are adapting the static initializer idea. Too bad the PHP folks won't.

Example:

  class Console extends Object {
    public static $out, $err= NULL;
    
    static function __static() {
      self::$out= new OutputStream(STDOUT);
      self::$err= new OutputStream(STDERR);
    }
  }

This was originally described in the XP Framework's RFC #0002 as early as November 2003

Five questions about language design

2006-11-24T23:58:24+01:00

There's a nice write-up of Paul Graham with some of his thoughts about
language design.

Some of topics he talks about are:

the quality of a language designed for use of yourself vs. the quality of a language designed for use of others

good languages should allow writing things brief

languages should not concentrate on being fast, but instead give their users tools to find bottlenecks in their application

You Need an Application to Drive the Design of a Language

C#'s "using" statement

2006-10-22T14:40:31+02:00

Having blogged about Python's new with statement (see ), I decided I'll also mention C#'s using() which is quite similar.

From the C# Reference:

Defines a scope, outside of which an object or objects will be disposed.

"with" elsewhere

2006-10-08T22:30:02+02:00

You might know the with statement from JavaScript or Pascal (where it saves a few keystrokes by "auto-importing" the object).

  Person.Name= 'Timm';
  Person.Id= 1549;

  {* equvialent *}
  With Person Do Begin
    Name= 'Timm';
    Id= 1549;
  End;

The XP framework also has with, not really as statement, but as a noop function:

  with ($p= &new Person()); {
    $p->name= 'Timm';
    $p->id= 1549;
  }

You could basically omit with () and the brackets, they serve no purpose except making the above bit more readable (especially when you're using lots of assignments or method calls on an object).

Now in Python, with serves a different purpose - in a quite flexible way: What's New in Python 2.5 - The 'with' statement.

Exceptions From Constructors

2006-09-18T22:04:46+02:00

Found the following while scanning throught the JavaSpecialists newsletter archive:

What is the best way to deal with objects that cannot be properly instantiated?

Ignore the problem and cause errors when you try to use the object later on
Throw a checked exception
Throw an IllegalArgumentException
Throw a NullPointerException
Throw an AssertionError
Put in a Java 1.4 assertion

Read the full article here.

exit() in Ruby

2006-05-26T22:41:48+02:00

While reading "Programming Ruby - The Pragmatic Programmer's Guide" I noticed the following:

The method Kernel#exit terminates your program, returning a status value to the operating system. However, unlike some languages, exit doesn't just terminate the program immediately. Kernel#exit first raises a SystemExit exception, which you may catch, and then performs a number of cleanup actions, including running any registered at_exit methods and object finalizers.

Imagine this:

  try {
    exit();
  } catch (xp~lang~SystemExit $e) {
    echo "Sourcecode tried to exit\n";
  }

For details and an example, see the Kernel#exit documentation.

So You Wanna Write A Unit Test

2006-05-20T22:00:40+02:00

Stumbled upon this while surfing around the blogosphere:
Five things to keep in mind while you are trying to work up the ambition to write that test:

Don't take all day
Silence, please
Skip catching exceptions
Don't write the War And Peace of test methods
Don't give up!

The original article is at Russ Olsen's Weblog

Error codes or Exceptions? Why is Reliable Software so Hard?

2006-04-30T12:02:00+02:00

A very fun and interesting read:

Error codes or exceptions? Like static vs. dynamic programming languages or how great David Hasselhoff is (most people say great, I say super-great), it tends to turn into a pointless argument ("Hasselhoff is super-great ASSHOLE!").

Continue reading @ damienkatz.net

Further reading