Wednesday, June 25, 2008

Replacing One Line with Two in Eclipse

Eclipse 3.4 is out today. In reading through the list of new features, I find one that I literally could have used yesterday.

Simply, I was doing a refactoring where I wanted to replace one import declaration by two, so my desired replacement text was two lines. Eclipse has a nice multi-file search/replace feature. However, I couldn't find or figure out if the replace text field would accept some syntax to indicate "I want a line break here." Trying the obvious \n resulted in a literal backslash-n.

In Eclipse 3.4, we can now use \R to indicate a platform-dependent line break, and \n and \r now work as expected. Usually I hate being on the bleeding edge, but this time I curse my reluctance to have been trying out the release candidates.

Tuesday, June 17, 2008


In relation to the release of Firefox 3.0, someone at work mentioned that we have screencasts too, and I was happy to see one where Theo shows off Luc Berthelet's version of Breakout. Theo scrolls through the code on the screencast, so by judicious pausing you can probably copy it, but I wish I could find the notebook somewhere, for, you know, research purposes.

In a serendipitous connection, Wikipedia tipped me off that in the past month or so Luc has broken out of his position at Electronic Arts to start Tir Nua, something in the virtual world line of goods. One of his new employees that he brought with him is a name familiar around my workplace, former Wolfram Research employee Sarah Flannery. I remember hearing Sarah give a talk last fall about the webMathematica-based Wiki she'd worked up for Sims Online players, and how she'd tackled the runaway inflation in the Sims Online economy (all sources and no sinks).

People like Luc and Sarah are fun users for Wolfram employees like me who consider themselves mainline software designers and like to see Mathematica applied more like a regular programming language in areas very different from what you might typically expect.

Wednesday, June 04, 2008

Picking a CLOS Implementation to Play With

Being provoked into trying to learn a bit more about CLOS's method of multiple dispatch, and wanting to find an implementation, led me on this search path in a few spare minutes:

1. Search Google for CLOS

2. Click, which is on the site of Richard Gabriel ("worse is better")

3. Click the intriguing title CLOS: Integrating Object-Oriented and Functional Programming

4. Read with interest on the first page the essence of multi methods:

A generic function, or polymorphic function as it is sometimes called, is one whose implementation depends on the types of its arguments. That is, the code that is executed for a particular set of arguments is mechanically determined by the types of the arguments.

In strictly functional languages, an operation is defined by a single, monolithic piece of code; any argument-type conditionality is expressed as code explicitly programmed in by the user. In contrast, the CLOS notion of generic functions supports automatic selection from among separately defined, typespecific implementational parts. Yet, from the client’s point of view, generic functions and traditional ordinary functions are called in the same way: The procedural abstraction barrier is still in force.

5. Start looking for implementations. Search reddit for "lisp implementations".

6. Click Common Lisp Implementations: A Survey.

7. The survey lists 11 Common Lisp implementations. Of these, only 5 are listed as available on the Unixes and Windows. Of those, only 3 do not have commercial licenses. Two of the remaining choices have weird names: Armed Bear Common Lisp, which does not look promising (its own home page says, under "Bugs", that "ABCL's CLOS is intolerably slow"), and Embedded Common Lisp (ECL). It's difficult to tell what immediately from Wikipedia or Google what kind of support has. But the remaining candidate, GNU clisp, appears to be in good standing, judging from the Wikipedia article (where it is claimed this is the platform Paul Graham used for Viaweb), and the Sourceforge stats which claim 100 downloads a day in the past week.

8. Find the Clisp site. Another Lisp site without an obvious Download link.