porges » tips

Pearls Before Piglets

Porges — Wed, 27 May 2009 10:40:31 +0000

While Googling my way through the interwebs, I came across the 2008 Western Australian Certificate of Education sample examination for Stage 2 Biological Sciences. It contains this diagram:

If you’re wondering, the entire hierarchy is drawn from Umberto Eco‘s novel Baudolino.

Refactoring in Haskell: Adding an Argument

Porges — Wed, 10 Dec 2008 03:44:47 +0000

Just a small tip on this: When you add an argument to a function that already exists you should check the existing usage of the function. Say you have this:

f x y z = ...

… and you want:

f x y z w = ...

First of all you should check the contexts where f is used. For example, if f is quite often used as an argument to map (fmap, <$>):

elsewhere xs = map (f a b) xs

If you naïvely add w to the end of the argument list you’ll end up with this instead:

elsewhere xs = map (\x-> f a b x c) xs

On the other hand, if you take a look at the usage of f you can decide that because f is often used to map over things, you can insert the additional parameter before the last, and end up with nicer code:

elsewhere xs = map (f a b c) xs

You may even discover that the existing f is used in a lot of lambdas that could be avoided by rearranging its arguments!

Vacuuming Firefox’s sqlite3 databases

Porges — Sun, 16 Nov 2008 23:56:39 +0000

Firefox 3 was running very slow for me, so I desperately tried this, thinking that it wouldn’t make much difference. I was wrong; there was a noticeable speed improvement. From a bash shell:

find ~/.mozilla -iname '*.sqlite' -execdir sqlite3 {} 'vacuum;' \;

A useful gedit macro for LaTeX

Porges — Wed, 30 Apr 2008 06:28:41 +0000

Builds and displays your current LaTeX document, and removes all the temporary file spam.

#!/bin/bash
TMPDIR=$(mktemp -td)
 
rubber -d --into "$TMPDIR" "$GEDIT_CURRENT_DOCUMENT_NAME" &&
mv "$TMPDIR/${GEDIT_CURRENT_DOCUMENT_NAME%tex}pdf" "$GEDIT_CURRENT_DOCUMENT_DIR"
 
if [ $? -eq 0 ]
	then evince "${GEDIT_CURRENT_DOCUMENT_NAME%tex}pdf" &
fi
 
rm -rf "$TMPDIR"