Month: January 2007

After reading A World of Endless Advertisements I thought it would be interesting to see the AdBlock Plus version next to the unblocked version.

How “ad-supported content” is supported without ads, I don’t know. But as Banksy says:

“Any advertisement in public space that gives you no choice whether you see it or not is yours. It belongs to you. It’s yours to take, re-arrange and re-use. Asking for permission is like asking to keep a rock someone just threw at your head.”

(Faintly amusingly I actually had difficulty writing this post because AdBlock blocked the images I was using because their name contained the word “ads”.)

I had to integrate a haskell program into an existing make-based intrastructure this week. After a few false starts I managed to proxy to cabal through make with the following Makefile. I also added a feature to copy the binary created to a “bin” folder at the same level as the src folder. I’ve used the Haq example name from How to Write a Haskell Program and my cabal setup is similar to the one described there. Trying to compile Setup.lhs or anything more complicated is a mistake and I am assured that runhaskell is portable.

all:
	runhaskell Setup.lhs configure
	runhaskell Setup.lhs build
	cp dist/build/haq/haq ../bin/

clean: 
	runhaskell Setup.lhs clean
	rm -rf ../bin/*

Haskell seems to be missing a String replace function. Text.Regex.subRegex seemed like overkill. So I wrote one. It actually works on any list, not just Strings.

replace :: Eq a => [a] -> [a] -> [a] -> [a]
replace [] _ _ = []
replace s find repl =
    if take (length find) s == find
        then repl ++ (replace (drop (length find) s) find repl)
        else [head s] ++ (replace (tail s) find repl)

Some examples:

*Main> replace "hello" "h" ""
"ello"
*Main> replace "hello" "l" ""
"heo"
*Main> replace "hello" "x" ""
"hello"
*Main> replace "100,000,000" "," "hello"
"100hello000hello000"
*Main> replace "100,000,000" "," ""
"100000000"
*Main> replace [1,2,3] [1] [9]
[9,2,3]
*Main> replace [4,5,6,1,2,3,7,8,9,2,3,6,5,4,1,2,3] [1,2,3] [10]
[4,5,6,10,7,8,9,2,3,6,5,4,10]

If this function is already in the standard libraries somewhere or if this can be improved in some way please leave a comment to let me know. Thanks!

A cautionary tale about installing debian-unstable packages under Ubuntu Dapper.

I needed version 6.6 of the Glasgow Haskell Compiler and Dapper/Edgy only supply version 6.4.2. I found a mailing list post explaining that 6.6 was available under debian-unstable, which is what Ubuntu is based on. So I downloaded the .deb and tried to install it.

No dice. Requires a partcular version of libc6. So go grab that (BIG mistake – this is possibly the most central library in the whole system and switching versions of it was never going to be a good idea). Try to install, find a dependency (tzinfo), try to install the dependency and kapow – failed in mid-install! Tried to overwrite a file that dpkg thought belonged to the locales package.

Now, whatever I did I got something like this:

sudo apt-get -f install
Reading package lists... Done
Building dependency tree... Done
Correcting dependencies... failed.
The following packages have unmet dependencies.
  libc6: Depends: tzdata but it is not installable
  libc6-dev: Depends: libc6 (= 2.3.6-0ubuntu20) but 2.3.6.ds1-10 is installed
  libc6-i686: PreDepends: libc6 (= 2.3.6-0ubuntu20) but 2.3.6.ds1-10 is installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
E: Unable to correct dependencies

I tried every combination of: apt-get remove, apt-get install, dpkg -r and dpkg -i with each package name and variations on the package names as well as bare apt-get install -f and using –force and –purge and goodness knows what else (many thanks to the denizens of #ubuntu on freenode for their many suggestions). Whatever I did the system would just tell me it was queueing up to install the debian versions of ghc and libc6 and that it couldn’t work it’s way out of the dependency pickle.

Finally a knight in shining armour by the unexpected name of “crot” came up with this baby:

sudo apt-get install -f libc6/dapper

The /dapper forces the system to install the correct version even though the debian package is also called libc6. Thanks crot!

I leave this blog post for those who try something equally foolish. If you use a package from the wrong distribution or wrong version, this may help you out.

Forget about Vista/Aero, just look at the visual abuses that are possible in the Ubuntu with AIGLX (coming as standard in Feisty in April 2007). Mostly pointless but tremendous fun.

(Mark Shuttleworth calls providing this kind of facility one of the challenges we need to overcome. He hopes to see usability/productivity enhancements as well as pretty bubbles and lines of fire. I hope so too.)