Some Common Lisp Tip Tweets

Posted on 2012-08-30 by jcs

Jean-Philippe Paradis over at HexstreamSoft has a very nice set of tweets on Common Lisp tips. For example, 【Meta+x】 slime-cheat-sheet opens a new frame with useful slime commands and their shortcuts. As Paradis remarks, this is virtually unknown—I sure didn’t know about it.

Another interesting tip uses the ldiff function to return the head sublist from member instead of the tail. Another thing I didn’t know. There’s a lot of good material in these tweets and well worth the time of any Lisper.

He also has some opinions that you may or may not agree with but, again, they’re interesting and he mostly gives his reasons for holding them. All and all a very nice resource.

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Upgrading to Emacs 24.2

Posted on 2012-08-29 by jcs

Just a quick note to announce that I just upgraded my Mac (OS X Lion) to Emacs 24.2 from source. The upgrade went without any problems so if you’re on a Mac, there’s no reason to wait.

From the top level Emacs source directory do 

./configure --with-ns
make install
sudo mv nextstep/Emacs.app /Applications

and relaunch Emacs. That’s all there is to it.

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Impatient Mode

Posted on 2012-08-29 by jcs

You may have seen some of the posts about Chris Wellons’ Emacs HTTP Server, an HTTP server that operates from within Emacs. Now Brian Taylor has built on that to provide Impatient Mode, an Emacs package that renders an Emacs buffer to your browser on the fly.

Taylor’s post has a video showing Impatient Mode in action. If you’re into instant gratification, you might enjoy using Impatient Mode—it’s a nice application of Wellons’ Emacs HTTP server. It’s probably not going to change your life but it’s a neat hack and can certainly be useful in certain situations. Take a look at Taylor’s post to see if it might be useful to you.

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The magic-mode-alist

Posted on 2012-08-28 by jcs

Most Emacs users know how to associate a file type with a major mode by using the auto-mode-alist variable to associate a file extension with a major mode. I recently learned of another way thanks to Xah Lee who posted a note on associating files with a major mode.

It turns out that you can use the beginning of a file to associate it with a major mode in much the same way that the Unix file command determines the type of file from the first few bytes of the file. To do this you add a cons of a regular expression matching the beginning of the file and the major mode to invoke to the magic-mode-alist variable. Lee gives this example to invoke nxml-mode for html files:

(add-to-list 'magic-mode-alist '("<!DOCTYPE html .+DTD XHTML .+>" . nxml-mode))

Emacs checks the magic-mode-alist variable before checking auto-mode-alist so the beginning of file check takes precedence. You can also specify a function instead of the regex to deal with situations too complex for a regular expression.

Lee’s post has a nice summary of all the ways Emacs can associate a major mode with a file so you should give it a look.

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Readable S-Expressions

Posted on 2012-08-27 by jcs

Why do people keep doing this? They should stop. Now. Really.

There is nothing wrong with parentheses. Lispers like them and deal with them without difficulty.

There is nothing wrong with Lisp syntax. Lispers like it and deal with it without difficulty.

There is nothing awkward about S-expressions. They are not hard to read and, really, those who find the prefix notation confusing or fail to understand its advantages should find another way to earn a living.

If you think Lisp should to be like Python, just use Python. The Lispers and Pythonistas will both be thank you.

If you’re going to quote Paul Graham, don’t use his words to make a point that he certainly wouldn’t agree with.

Afterward:

Reading this over, it may seem a little harsh. Certainly Wheeler is entitled to work on any project he likes and to scratch anything that itches but I don’t see the point of this project. It tries—unsuccessfully, I think—to fix things that Lispers don’t see as broken and produces a syntax that starts with the clean and elegant Python and makes it ugly. Actually, I think Pythonistas should be more offended than Lispers at the result.

To paraphrase DMR, if you want Python, you know where to find it.

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Emacs

Posted on 2012-08-26 by jcs

It’s everywhere!

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The Emacs Manual in Info

Posted on 2012-08-25 by jcs

This is definitely a note to myself. Doubtless everyone knows this but for some reason I can never seem to remember it so I am recording it in a post. If you’re an Emacs user and your initials are not RMS, you probably have occasion to consult the Emacs manual. When I find myself in that position I most often just bring it up in my browser. That’s easy because I have it book marked but it’s also a little silly since Emacs has the manual built in.

Of course you can always do 【Ctrl+h i】 and then pick the Emacs manual entry but there’s a better way. You can bring up the manual directly with 【Ctrl+h r】. That’s almost no savings in labor but somehow it seems much quicker and easier. At least it would be if I could remember it.

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Lena

Posted on 2012-08-24 by jcs

I ran across this astounding story of Singapore researchers at Singpore’s Agency for Science, Technology and Research generating a digital image with 100,000 DPI resolution. This is close to the theoretical maximum resolution and is therefore a significant achievement.

What impressed me, though, is the backstory of the image itself. The picture is of Lena Söderberg, a Swedish model who was a 1972 Playboy centerfold. This picture is a standard digital image that researchers use for experimenting with new digital algorithms and has been used for 40 years. The picture was originally chosen when researchers needed an image to scan for a paper. They looked through the standard stock images but everything seemed boring. At that point, somebody walked in with the current issue of Playboy and the researchers tore off the top third of the image so that it would fit on the drum of the scanner and an icon was born.

In 1997, Lena attended the 50th Anniversary of the Society for Imaging Science and Technology conference and met many of the scientists who have been using her picture for 4 decades. She’s now happily married with 3 children and works for the government. It wasn’t until 1988 that she first learned what had happened to her picture. She’s said to have been pleasantly amused. At the conference she commented to a Wired reporter, “They must be so tired of me … looking at the same picture for all these years!”

None of this is important, of course, but it is a charming story that gives us a glimpse into the real person behind a standard and well known test image. You can read more about Lena’s story by following the above links.

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Scientific American on Piracy

Posted on 2012-08-23 by jcs

David Pogue over at Scientific American has an interesting article that makes a point that most Irreal readers are familiar with: Hollywood encourages piracy by not making movies available legally. Pogue points out that many popular movies are not available to rent online and that none of the 10 most pirated movies can be viewed online legally. The result of this, of course, is that users—who are not at all inclined to be denied—simply download the movies illegally netting Hollywood no income from the viewing.

It doesn’t have to be this way. The music industry has already figured this out. Some people will pirate regardless of availability but the vast majority of people simply want to see the movie and would happily pay for it if it was available. Of course, this is well known and was neatly captured by the now famous Oatmeal cartoon. The industry mumbles about existing agreements and protocols as if these things were out of its control. Of course, they aren’t—it’s Hollywood for goodness sakes.

As I said, none of this is news to the people around here but it’s significant that we’re now reading these opinions in organs such The New York Times and Scientific American. It’s one thing to have nerds pointing out the obvious but quite another when the establishment media starts mentioning the same inconvenient truths.

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Jon Bentley on Quicksort

Posted on 2012-08-22 by jcs

One of my heroes in Jon Bentley. If you don’t know who he is, this post is for you. If you do know who he is, this post is also for you. Bentley is one of the original Bell Labs researchers from the Lab’s golden age. Many of you will know him through his Communications of the ACM Programming Pearls columns and the three books that recapitulated those columns.

Bentley is a guy who is vitally concerned with algorithms and how to optimize them. If you haven’t read Programming Pearls and the two sequels, you’re really missing out. I can’t emphasize enough how influential these books were on my development as a programmer. If you haven’t read them, you need to do so immediately. Really.

Bentley recently gave a talk at Google in which he attempts to answer the question “What is the most beautiful code you’ve ever written?” Being Bentley, the answer is not simply X but rather a careful and extensive exposition of his reimplementation of the quicksort algorithm. Nothing I could say can begin to give justice to this talk. It is, really, a distillation of what makes Bentley Bentley. You really MUST watch this video. Believe me, you won’t be sorry. This is a great talk and you WILL learn a lot.

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