Skip to main content


Showing posts from December, 2008

Vim: ctags

ctags is a tool that figures out where various functions, classes, etc. are defined. Using ctags, you can use a hot key to jump to the definition of the symbol under the cursor.

To get started, install exuberant-ctags. In Ubuntu, this is just "apt-get install exuberant-ctags". Now, from within Vim::cd project_root
:!ctags -R .
:set tags=tagsTo jump to the definition of the symbol under the cursor, use cntl-]. To get back to where you were, use cntl-o.

There's also a taglist plugin for Vim. Once you install that, you can use ":TlistToggle" to open up a window on the left that shows all the things defined in your open files. I have that mapped to "T" by putting the following in my .vimrc: "map T :TlistToggle<CR>".

Thanks to Benjamin Sergeant for helping me get started with ctags.

Editors: I Dig Komodo Edit

I think I'll switch to Komodo Edit for editing HTML, CSS, JavaScript, Python, Ruby, Perl, and PHP. I'll still use Vim for random text editing and for editing my outline files, and I'll still use Emacs for editing Erlang, Haskell, and Lisp, but I think Komodo Edit is better suited for Web programming.

This is going to be a fairly long review, so let me break it down into sections:The Good PartsOne thing I really like about this editor is that it is more sophisticated than a default installation of Vim or Emacs, but less sophisticated than a full-blown IDE. I don't feel overwhelmed like I do with Eclipse. The download is only 37mb compared to 134mb for Aptana Studio, and you can really feel the difference. So far, it's been very easy to learn and use rather than feeling frighteningly complex.

Let's start with the basics. As you might expect, it does a beautiful job highlighting the various languages. It handles HTML that contains JavaScript and CSS quite easi…

Emacs: nXhtml

In response to the comments in Software Engineering: The Right Editor for the Right Job, I took a look at nXhtml for Emacs.

The scope of nXhtml is impressive. Take a look at the picture. This is a snippet of HTML / JavaScript that I was testing as a part of something else. I hit tab on every line to make it indent things. nXhtml isn't getting the indentation perfectly correct, nor is it getting the syntax highlighting completely correct (why is "beacon" in red?); however, this is worlds better than what comes with Aquamacs by default.

I think nXhtml is a promising project.

Next up, I'm going to check out Komodo Edit. It does make sense to me that since Emacs is written in Lisp, it would be one of the best editors for Lisp, whereas since Komodo Edit is based on XUL (aka Firefox), it would be one of the best editors for editing HTML, CSS, and JavaScript. Of course, I'll have to wait and see.

Software Engineering: The Right Editor for the Right Job

Imagine if you were reasonably skilled with all text editors and all IDEs. Which would you prefer for which tasks?

Clearly, if you're coding elisp, Vim would be a bad choice. Of course, what would be the point? More seriously, Emacs is written in Lisp and has SLIME, the Superior Lisp Interaction Mode for Emacs. Duh, no brainer.

For Scheme, there's something nice to be said about DrScheme's editor. Although, if we stick with the premise of knowing all text editors reasonably well, I'm guessing you might still stick with Emacs.

However, Emacs isn't perfect for everything. For instance, it my have a built-in Web browser, but I can guarantee you that I won't be giving up Firefox just so that I can use Emacs form widgets.

Similarly, Emacs is a little weak on the HTML, CSS, JavaScript side. Aquamacs comes with a fantastic mode for Latex, but if you want to edit an HTML file that has CSS and JavaScript in it, it's less than pleasant. mmm-mode and nXhtml-mode a…

Web: Robust Click-through Tracking

I have a web service that provides recommendations. I want to know when people click on the links. The site showing the links (imagine a book store) is separate from my web service.

Let's imagine a situation. My server generates some recommendations. The site shows those recommendations. After 10 minutes, my server goes down because both of my datacenters go down. I want to know if the user clicks on a link, but if my server is down, that must not block the user from surfing to that link.

I see how Google does click-through tracking. It's simple, non-obtrusive, and effective. However, as far as I can tell, it requires the server to be up. Well, they're Google ;) It's different when you're a simple web service that must never ever cause the customer's site to stop working.

I came up with the following:<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"


Python: Web Beacons in Pylons

A Web beacon is usually an image tag that refers to a 1x1 clear gif on a remote server. The remote server is able to track that the gif was seen when the browser tries to download it. If you're using Pylons, here's how to implement that beacon in a way that won't be cached:CLEAR_GIF = 'GIF89a\x01\x00\x01\x00\x91\xff\x00\xff\xff\xff\x00\x00\x00\xff\xff\xff\x00\x00\x00!\xff\x0bADOBE:IR1.0\x02\xde\xed\x00!\xf9\x04\x01\x00\x00\x02\x00,\x00\x00\x00\x00\x01\x00\x01\x00\x00\x02\x02T\x01\x00;'
def some_action(self):
# Do interesting things here...
response.headers['Content-Type'] = 'image/gif'
response.headers['Cache-Control'] = 'no-cache'

Python: Timesheet Calculator

Little programs are so much fun to write ;) Here's one that adds up the hours in my time sheet.#!/usr/bin/env python

"""Add up the hours in my hours.otl file.

The file should have the following format::

3.25 hours working on project-specific domain names.

The date must be in margin 0. The number of hours must be indented.


nosetests --with-doctest

Note, I'm positive that this script could be replaced by a one line
awk script, but whatever. It was fun to write.


from cStringIO import StringIO
from optparse import OptionParser
import re
import sys

TEST_DATA = """\
7 Hours programming.

8 Hours hacking.

hours_regex = re.compile(r"^\s+([0-9.]+)")

__docformat__ = "restructuredtext"

def process_file(f):
"""Add up and return the hours in the given open file handle.

This may raise a ValueError if the file is malformed.


Emacs: vimoutliner

I've been drinking too much caffeine lately, and if you know me, you know what that means--I start getting weird urges to play with Emacs.

One of the things that always drives me crazy about Emacs is indentation. It's hard to get it to do what I want it to do in cases where there is no mode that matches what I'm coding. I have a ton of files written using vimoutliner, and I don't feel like switching them to Emacs' own format. It's a simple outline format. Four space wide tabs are used for nesting.

I could never figure out how to get Emacs to just "do the right thing" with these .otl files. I finally figured out the right magical incantation, thanks to some hints from Jesse Montrose. Updated:;; Add support for Vim outline files.
(defun otl-setup ()
(setq outline-regexp "\t+")
(setq indent-tabs-mode t) ;; Use real tabs.
(setq tab-width 4))

(setq auto-mode-alist
(cons '("\\.otl$" . outline-mode)

Python and Ruby: Regular Expression Anchors

In Python regular expressions, multiline mode is off by default. The documentation says:When [multiline mode is] specified, the pattern character '^' matches at the beginning of the string and at the beginning of each line (immediately following each newline); and the pattern character '$' matches at the end of the string and at the end of each line (immediately preceding each newline). By default, '^' matches only at the beginning of the string, and '$' only at the end of the string and immediately before the newline (if any) at the end of the string.In Ruby regular expressions, the multiline modifier (m) is also off by default. However, '^' still matches the beginning of each line.

Hence, in Python, the following does not match:re.match(r'^foo', '\nfoo\nbar')Interestingly enough, this does not match in Perl either:"\nfoo\nbar" =~ /^foo/In Ruby, it does:/^foo/.match("\nfoo\nbar")Both Python and Ruby support …

Computer History: Doug Engelbart

I went to a talk yesterday. It was the 40th anniversary of Doug Engelbart's 1968 "mother of all demos". In the demo, Engelbart demonstrated:The first computer mouseThe first graphical user interfaceThe first personal, interactive, networked computerThe first use of hypertext (i.e. text with links)I had heard about the demo but never watched it. It's available on YouTube, and it's definitely a must see. Doug had a grand vision of using the computer as a tool to help people accelerate how quickly they could solve problems. That goal has always fascinated me.

Robert Taylor, whose funding led to the creation of the ARPANET, told a pretty good joke, which he himself said was probably apocryphal. Rather than retell it, I grabbed a copy from here:Whenever you build an airplane, you have to make sure that each part weighs no more than allocated by the designers, and you have to control where the weight it located to keep the center of gravity with limits. So there i…

Books: RESTful Web Services

I just finished reading RESTful Web Services. I'll summarize. At its worst, it was boring and dogmatic. At its best, it helped me to formalize my understanding of REST, and it gave me a protocol-level introduction to a variety of topics like the Atom Publishing Protocol, microformats, S3,, HTML 5, etc.

One thing I found particularly frustrating is the author's attitude toward RPC. Basically, his stance is that RPC is synonymous with all things evil. Consider the following quote:This is why making up your own HTTP methods is a very, very bad idea: your custom vocabulary puts you in a community of one. You might as well be using XML-RPC. [p. 105]Ok, so using XML-RPC is just as bad as sending "EAT / HTTP/1.0" to a server. WTF?

I've implemented services using CORBA, JRMI, XML-RPC, and a couple times with REST. At the risk of calling the emperor naked, I liked XML-RPC the most. REST might look nicer at the wire level, but at least in Python, XML-RP…

Grammar: Predicates

I've noticed that certain programmers love grammar, so I hope you won't mind the following:

"The predicate is the subject of this sentence."

What's the subject? "The predicate" is the subject of this sentence.

What's the predicate? The predicate is "is the subject of this sentence."