Category: Hacking

Programming and related activities.

Making Emacs Do Stuff at Startup

Like many users, I start an emacs session in .xinitrc and use it throughout the day. Since I’ve recently started using Emacs Planner, I wanted it to start up automatically in that first Emacs session (but not subsequent ones, if I just want to edit a file).

Continue reading “Making Emacs Do Stuff at Startup”

Soft Coding

Over at Worse Than Failure, Alex Papadimoulis has an article on soft coding. Hardcoding is when something is written in the code when it ought to be in a header constant or an external config file. Soft coding is the opposite, when something is put in a config file that really ought to be in the source. For instance, the number of days in a week isn’t likely to change any time soon, so you may as well just use “7” in your code. You might

#define DAYS_PER_WEEK 7
#define WEEKS_PER_YEAR 52
#define LOAN_DURATION DAYS_PER_WEEK * WEEKS_PER_YEAR

to make it clear what you’re calculating, but putting it in an external, user-configurable file is just absurd.

I’m guilty of softcoding, myself. In my experience, it comes from trying to be too generic. Code that’s too specific, too hardcoded, is hard to maintain and extend, so a good programmer will ask himself, “What requirements might change in the future? How should I write this so that when it changes, I can do it without too much pain?” This leads to things like declaring configuration constants at the top of a script, in a Makefile, or in a header file; or having the code read messages from an external file, rather than hardcoding them as strings.

But it’s also easy to overcompensate, and start making everything customizable, or overly generic. So it’s important to remember that at some point you have to actually make the code do something.

Removing Accents in Strings

I’ve been ripping and encoding a bunch of music. Since I’m a hacker, naturally I have scripts that take a file with artist, album title, and track titles, and finds the corresponding .wav or .aiff source files, encodes them as MP3 and tags them.

A lot of the music I have is in French or German (and some Spanish and Russian), so there are accented letters in names and titles. My input files are in UTF-8 format, so that’s cool. But one problem is that of generating a filename for the MP3 files: if I want to play the song “Diogène série 87” by H.F. Thiéfaine on his album “Météo für nada”, I don’t want to have to figure out how to type those accents in the file and directory names. I want the script to pick filenames that use only ASCII characters.

Continue reading “Removing Accents in Strings”

How Do You Spell the Names of the Months?

One construct that I’ve seen (and used) a lot in Perl is a hash that maps month abbreviations to numeric values that can be fed to POSIX::strftime:

our %months = (
    "jan" => 0, "feb" => 1, "mar" => 3, ...
);

This is useful for parsing log files and such. It works, it’s quick and easy, and it doesn’t require a whole tree of dependent modules (which are always on the wrong side of the Internet) to be installed.

But what’s always bugged me is that this is the sort of thing that the machine ought to know already. And besides, it’s US-centric: what if the person running the script is in a non-English-speaking country?

Fortunately, I18N::Langinfo knows the names of the months. Continue reading “How Do You Spell the Names of the Months?”

How to Write A Good API

A lot has been written about how to design a good user interface, but very little about how to design a good programming interface (API: Application Program Interface, or a library). This is somewhat surprising, since an API is nothing more than an UI for programmers, and programmers are normally good at writing tools for each other.

Continue reading “How to Write A Good API”