Older blog entries for chalst (starting at number 119)

News sources
berend wrote: That's why I love blogs. News can no longer be ignored or hidden.

That's a thought that unites Berend and Raph, despite the different types of news that makes them happy when it breaks out from behind the media skirts. Pessimistic thought: appearing in a blog doesn't mean a news story has made it to the wider social awareness. Blogs are still obscure, and precious few stories are successfully nurtured to the point where mainstream news media are forced to take note of them.

Optimistic note: there's now news sources for lots of the emerging topics I'm interested in, and I can now bring my expertise to ears that would not otherwise hear it. I'm now a contributing editor at Ehud Lamm's Lambda the Ultimate (not yet made use of the privilege), and am a founding member of a team of a to be soon launched group weblog on the contact area between computer science and philosophy; here is the announcement.

And on the crucial question: which is the best news source for international issues: NYT vs. WaPo? Josh Marshall weighs in, saying:

Over time you get a good sense of which news outlets consistently generate new information and which don't. And by this measure -- on the issues I follow closely, which I'd say are foreign policy, defense policy, intelligence and national politics -- the Post consistently outclasses the Times, particularly on the first three topics. When it comes to who's generating fresh information rather than summarizing the story a few days later or relying on hand-fed stories, my experience putting together this site tells me I usually end up finding new information -- which stands up over time -- in the Post.

My own take: I've never liked the NYT, it always has a parochial feel when reporting foreign news (especially Germany: I don't recall ever reading an article on a story in Germany in which Nazis were not at least alluded to); the WaPo is infinitely better in this regard, and as Josh says, you have the sense that you are reading the stories by people who have done the spadework. I prefer the Financial Times to both, btw.

Liskov Substitution Property
graydon writes on the failure of object oriented programming languages to enforce the Liskov substitution property. I tend to make very limited use of OO in my programming, but I wonder how bad the lack here is. Oleg's example is easy to solve: what one would do is have each class inherit from a common abstract class; my guess is that LSP violations hardly ever occur in code written by experienced OO programmers (an analogous point would be violations of occurs-check in Prolog code: it happens rarely enough that Prolog implementors think it is not worth the overhead of defining unification to detect occurs check violations).

Graydon also says this issue lends further evidence to my belief that language design is actually regressing: even better evidence for this is the corruption of `lexical' scoping in Python, a disease which I note has spread (hint: lexical scope is entirely determined by the syntactic structure of the source code).

Copenhagen Consensus
In a piece of underreported news, Bjorn Lomborg has announced he will step down as chair of the Danish Environmental Assessment Institute. John Quiggin has two pieces assessing his major achievement in this time: part one criticising the composition of the panel, and part two criticising the idea of trade offs implicit in the latter. He's surely right on the first point, but on the second, I'm not sure that coming up with a cost-benefit ranking does presuppose the picture of trade offs Quiggin criticises; instead it can tell you in what direction we should be pressuring for change.

On a general point, I think Quiggin is the best blogger on matters of environmental economics.

Congratulations fxn!
Congratulations on the birth of your daughter!

Server up
Has it really only been six weeks? It's absence is a reminder how much I value this place: thanks to all who helped bring it back. Nice to see permalinks on recentlog.

Computer Science Weblogs
In the meantime, something has happened at Lambda the Ultimate: it was one of the sites slated to close down with the changes at Manila, and has moved to lambda-the-ultimate.org, on a new server. There's been a big improvement in response time, and the site has had a bit of a facelift.

Computation weblogs
An addition to my "Computer science weblogs", whose home has moved to www.linearity.org/cas/weblog/complogs.html, and whose name has changed to "Computation Weblogs":

Andrew Birkett's blog, subtitled "Thoughts of a software engineer", has a heavy programming languages design and implementation slant, and is generally excellent:

• Optimization asks the question "Why do programs have to get more complicated when you try to speed them up?" and why is it not possible to write code rather like *ML and XML transformers, so that one writes a simple program that is readable, maintainable and easy to reason about, and transformations on this code that make it into efficient code.
• Yet another compiler compiler and and It's MetaTurtles, all the way down gives a nice introduction to the idea of automating the process of compiler production by starting from formal specifications of the programming language.

  Nice, but I have to quibble: Andrew asserts of denotational semantics: Unfortunately, having all these mathematical objects and theorems floating around isn't getting you much closer to having a compiler for the language, which simply isn't true: a denotational semantics provides you with the recipe for automatically generating an interpreter, which in principle can automatically transformed into a compiler by partial evaluation. The real problem with denotational semantics is that it's proven difficult to provide them for non-toy languages.

• Of limited scope and Predicate objects talks about some issues around variables whose meaningfulness varies through their lifetime.
• Monads by stealth motivates a C++ abstraction that turns out to be the same thing as a paradigmatic monad.

Graydon's recent thoughts on pointers
I don't share graydon's dislike of garbage collection (in particular, functional programming becomes tiresome with explicit memory management), but I do think there is a lack of languages that allow garbage collection, allow user control without any enforced runtime, and allow one flexibility in choosing mixtures of the two (Scheme48/prescheme sort of allows this, but the runtime is not optional, and the mixing is not flexible or convenient). In particular I would like to see a language where one could, without undue pain, transform code written assuming garbage collection into code with explicit memory management. There's a lot of know-how of how to do this is the scheme community

graydon wrote:

I believe there is some relationship between this approach and the "linear naming" research that chalst is doing.

There is definitely a similar way of thinking going on, although some important differences:

• The implementation of "linear names" has always been as reversible pointers, ie. each pointer points to a back pointer; pointers are usually implemented as pairs of C pointers to data structures plus offsets to the backpointer, allowing several reversible pointers to point to the same data structure; thus names are not quite the same thing as ownership;
• There are no weak pointers in anything written or implemented. Alan Bawden and I thought of adding them, they would have uses, but nothing was ever done. Instead sharing is done explicitly, by having special data structures that allow the data structure to be connected to arbitrarily many users by means of sharing trees. This is related to the way proof nets are handled for linear logic, hence the "linear" in linear naming.
• We are happy with cycles, but then we are not trying to eliminate garbage collection (yet); disconnected subgraphs are garbage. There is a resource management problem since data structures may span many hosts and may move unpredictably; there's a fairly easy solution, but possibly ideas such as yours could improve on that.

A Security Kernel Based on the Lambda-Calculus
I've linked to Jonathan Rees' 1995 PhD thesis before, but am plugging it again, since it was mentioned on Lambda the Ultimate.

Advice on learning mathematics
Turns out I'm writing diary entries less often than graydon these days... I can only half-blame not having time due to the baby, since I am finding time to spend on Orkut (ncm introduced me to it almost four months ago). I just posted a reply to a query for advice on starting study of mathematics from the Orkut Mathematics forum; maybe it has wider appeal:

• Recognise that cultivating an intuition of mathematics and knowing how to give rigorous proofs of mathematical theorems, while related, are quite different kinds of knowledge, and mathematical intuition is more fundamental;
• Learn to judge whether mathematics is good, whether it is powerful or beautiful, and not just whether it is correct;
• The best way you can spend time is find someone with similar tastes in mathematics and spend time regularly with them discussing problems, papers you have read, crazy ideas you have had, and so on. I didn't do this until I started my doctorate; now I regret....
• Leverage what you know: because you are confident with programming, try coding up programs that find witnesses to existential theorems you prove. There's a close analogy between proving theorems and writing programs.
• Don't make the mistake of just choosing computer-relevant mathematics: the core subjects of mathematics complement each other and were you to avoid analysis, say, you would finish your degree with only a skewed and incomplete grounding in mathematics.

The ZF inconsistency proof of the day
Brian Ford and Randall Holmes are discussing Ford's claim on the FOM list. It's still up in the air, but it looks like (i) Ford's argument is interesting, and (ii) there is an argumentative hole in it.

My own investment in the question: I'd rather like ZF to be consistent, but I wouldn't be upset if it wasn't. You can avoid worries about strong axioms by using only geometric theories in your basis theory (or metatheory, if you prefer); these can be shown by simple proof-theortic means (cut elimination) to be consistent, and IIRC they can capture all Pi^0_1 consequences of any consistent theory, or in other words, they can be quite strong but are never too strong.

BabyBlog
Carlin made her first strike against the system on May 1st, with an exercise of public nudity in the Tiergarten. She seems to have a talent for autonomiste activism. She's 15 weeks old tomorrow.

Posctscript: Ah, just read fxn's entry: he beat me to the above by two days, but there's extra information in my entry... There's actually something of a literature of correct-seeming ZF inconsistency proofs; someone should write up the history of them.

graydon wrote:

I think the idea of a "software component" is a wrong and damaging distraction from a fundamental fact: program text is the ultimate component technology.

I almost completely agree, but actually I think there's nothing wrong with a properly thought through VM model of exchangeable code. No doubt, though, improper application of the component mindset has very widespread and farreaching consequences, almost all malignant.

BTW, I completely agree with what you said about language wars, though if we were forced (at gunpoint, naturally) to choose between C# and Java, I think Java has to be the choice. Mono, I think, is a very, very, dangerous thing for GNOME.

BabyBlog
Carlin will be six tomorrow. Six weeks, that is.

Recentlog
First time I've read recentlog from beginning to end in, well it would be since about six weeks ago...

ncm: Thanks three times for your congratulations messages, and it is excellent to see such finely calculated mischief as the "I Hate Java" community at Orkut. I almost wish I was a Java hater myself...

And re monotone: indeed, and not only is it well coded, the design is deeply revolutionary. Hackers of the world unite, you have nothing to lose but your beauty sleep! Join the revolution now, while you can be one of its heroes...

fxn: Thanks and congratulations yourself. BETA around 120 days? That should be in an easy patch IIRC :>

badvogato: Quite so, but I posted on the 25th and was wishing my readers a happy new chinese year. Carlin indeed falls under the sign of black sheep/goat, and since she is also a Capricorn, astrologers might get a bit excited about her goaty spiritual influences.

Carlin Stewart-Wiese
Our baby daughter was born late on Tuesday night (20th January), at 10:55 pm (Berlin time), weighing 3.38kg (7lbs 7oz), and 51 cm long. You can see a photo of her.

The birth was very tough on my wife, but she's recovering well, and Carlin is healthy, happy and hungry.

And happy year of the monkey, everyone...