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Note:These pages make extensive use of the latest XHTML and CSS Standards. They ought to look great in any standards-compliant modern browser. Unfortunately, they will probably look horrible in older browsers, like Netscape 4.x and IE 4.x. Moreover, many posts use MathML, which is, currently only supported in Mozilla. My best suggestion (and you will thank me when surfing an ever-increasing number of sites on the web which have been crafted to use the new standards) is to upgrade to the latest version of your browser. If that's not possible, consider moving to the Standards-compliant and open-source Mozilla browser.

September 28, 2010

A Bit of Undesired Excitement

Campus was locked down today. Classes were cancelled. And, most annoyingly, the café in the RLM lobby was closed. Despite rumours of a 2nd gunman, it seems there was only one person (and an AK-47) involved and, mercifully, he was the only casualty.

Posted by distler at 3:25 PM | Permalink | Followups (3)

Instiki 0.19

After much delay, I’m releasing Instiki 0.19.

It’s been 9 months since the previous release, so – naturally – there’s a lot of new stuff to report.

The most visible change comes when you unpack the distribution. External dependencies have always been a pain to deal with. With Instiki, we’ve tried to minimized their number; but sometimes they’re unavoidable. With Instiki 0.19, I’ve started using Bundler to manage external dependencies. What that means is that, when you’ve unpacked the distribution, you need to type

ruby bundle

at the commandline, from the main Instiki directory. This will download and install the Rubygems used by Instiki. The list of Rubygems is in the Gemfile. And, if your situation is special, you can tweak that list. If, for instance, you’re using MySQL instead of the default sqlite3 database, you need to add a line

gem "mysql"

to the Gemfile. Users on Dreamhost will find that they need to modify the entry for sqlite3-ruby. But, in general, you should find that you won’t have to muck with it and that the whole installation experience is more hassle-free than before.

The next most visible change is that itex2MML is now a Rubygem (managed by Bundler), so you don’t need to worry about installing it separately. In fact, with 0.19, every Instiki installation now provides an itex-to-MathML translation service as a web service. Perhaps, you’ll find other uses for it, but the main reason for its existence is that …

Instiki now includes a WYSIWYG drawing package, based on SVG-Edit. You can embed SVG figures directly in your wiki pages, and you can embed MathML content in those SVG figures. This has proven really useful to me, personally, what with the ability to export Instiki pages to LaTeX, and export the figures to PDF.

This release is based on Rails 2.3.9. I expect that the next release will be based on Rails 3.

Update: Nested Extensible Arrows

Thanks to some discussions with Frédéric Wang (of Mozilla MathML fame), I’ve improved itex2MML, so that it can now accommodate nested extensible arrows with optional arguments. Users of Instiki 0.19 can update their version of itextomml by typing

ruby bundle update

Posted by distler at 12:44 PM | Permalink | Followups (27)

September 21, 2010

Going Galt

A certain Professor Xxxx has received quite the internet thrashing for complaining that (cached version) — despite a household income (roughly $450K $400K ) nineeight times the median US household income — he’s really just an ordinary Joe, trying to make ends meet, and will suffer terribly if Congress allows the Bush tax cuts (on incomes over $250K) to expire.

I’m somewhat loath to pile on, as surely every cognitive flaw, exhibited in the post in question, has been more than amply exposed. But something struck me about one of his followup posts (cached version), which seems to speak to a more general bit of nonsense that one hears from those of Professor Xxxx’s ideological persuasion.

He says

So why doesn’t Prof. Krugman say that I’m a whiny loser because I’m complaining that the government needs 50% of the money I spend each month, on things like art camps? It may be that some of the decisions I made that led to these fixed costs were mistakes, but there will be a real impact from this increase in my tax burden. I’ve not seen any critic point out why my Polish-American house cleaner would be better off getting handouts from the government than earning her wage cleaning our house.

Now, arguing that your taxes shouldn’t be raised because, if they are, you’ll respond by employing fewer domestic servants, is probably not the winning sort of argument that a University of Chicago Law professor would teach his students to marshall. But let’s leave that aside. What I want to focus on is the fact that art camp, for apple-cheeked Amy is in peril. Two paragraphs later, he says

Fifth, lost in all of this is the impact of increased taxes on the work-leisure tradeoff. As marginal taxes rise, so does the disincentive to work. I’m asked with some frequency to write, consult, or testify, and when I do, I face the question of whether the effort and time is worth it. I can choose to watch the Steelers or help a hedge fund with a corporate law question. The higher my marginal taxes, the more likely I am to choose the former. This is a losing proposition from a social welfare perspective, no matter what you think of the quality of my advice or the role of hedge funds.

Let’s understand what’s being said here.

If his marginal tax rate is raised from the current 35% to 39% (the rate that prevailed during the Clinton Era), art camp for apple-cheeked Amy will become unaffordable. But, rather than take on that additional consulting gig (which, after taxes, would net him $122/hour, instead of $130/hour) to pay for Amy’s art camp, Professor Xxxx plans to sit on the couch watching football.

Is that really how Professor Xxxx plans to meet this (alleged) financial challenge? If so, he truly does inhabit a different psychological universe. Most of us, when cash-flow gets tight, try to find ways to increase rather than decrease our income.

But, really, who (except for the Xxxx’s) cares whether apple-cheeked Amy gets to go to art camp? What really matters to the rest of us is Professor Xxxx’s contributions to the overall economy. Is it really true that he (and others in his position) will park himself on the couch, watching football, instead of contributing productively to the economy?

Is it really true that raising the top marginal tax rate will hurt GDP, because people like Professor Xxxx will work less hard in response?

Posted by distler at 10:44 AM | Permalink | Followups (20)

September 5, 2010


My last paper was written almost entirely on an Instiki wiki, transferred to a TeX file (in an SVN repository) only a few days before submission. The 136 figures were prepared using Instiki’s nifty built-in WYSIWYG SVG-editor.

Unfortunately, when it came time to “export” the figures to accompany the TeX file, I realized – to my horror – that there did not exist a tool for converting SVG, with embedded MathML, into PDF. We ended up producing PNG bitmaps (essentially, taking screen shots in the browser). That was time-consuming (thank heavens for a graduate student co-author) and the results were less than completely satisfactory.

So, with the paper squared-away, and the semester well underway, I sat down to put together a better solution.

Posted by distler at 4:34 PM | Permalink | Followups (14)