(An additional note on the new blog)

24Apr08

I’m studying modal logic with the  Konyndyk textbook and (the philosophical aspect) of kripkean semantics with “Naming and necessity”. That should be a factor on deciding whether the new blog goes or not to planet haskell, as the recent drug-oriented material isn’t representative of *everything* I like about the world.

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I shall no longer be blogging here

24Apr08

I’m moving all my blogging activity — I even transported the posts and comments from here — to dayvancowboy.org.
 
Whether the address at Planet Haskell should be changed is a judgement call on the Planet Haskell admins as the new blog contains vast amounts of nonhaskell material, (there is some maths though), but basically anyone who [...]

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Is last.fm leaking information to Google?

04Jul07

I use last.fm, which means in effect I’m giving up large ammounts of privacy — the kind of music I listen to — for the sake of social networking (which in the end I don’t use at all) and fun stats. And that’s okay; at least the terms of service assure me that
We won’t [...]

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This might or might not qualify as a theorem prover

13Jun07

Just been implementing sentential logic as I progress through the textbook.

module Main where
import Control.Monad

data Formula a =
Prim a
| (Formula a) :+ (Formula a)
| (Formula a) :* (Formula a)
| (Formula a) :-> (Formula a)
| Not (Formula a) deriving Show

(<->) :: (Formula a) -> (Formula a) -> (Formula a)
a <-> b [...]

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Magic Caesar autodecipher

13May07

import Char
import List
charRot r w = let base = (if isUpper w then 65 else 97) in
if (isAlpha w) then chr (base + (mod ((ord w) – base +r) 26)) else w
strRot r w = map (charRot r) w
unRot w = [strRot r w | r<-[1..26]]
countString st = [length (filter [...]

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Simple linear analysis of the performance of two algorithms.

04May07

I’ve mentioned over and over and over again that I’m not a programmer, but a econometrician. Today we put that to good use.
1. The problem
I can think of two ways of producing the list of divisors of a number:

divisors x = [ y | y<-[1..x], (gcd x y) == y]
fdivisors x = [ y | [...]

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A quick me-too and a suggestion

03Mar07

First of all, let me get this out of my system:

Ok, now I have one more reason not to move out from WordPress.com
The LaTeX people should, by now, have a simple “web” version of LaTeX that can be easily installed by dropping files in your cgi-bin directory. The vast majority of people with hosting services [...]

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A slightly better function-DOT dsl

24Feb07

In some of the graphs in Bycicling for Collatz (the divisibility graph with lots of arrows and the collatz one with 1, 2 and 4 highlighted) we manipulated the Haskell-generated graph either in the DOT file source or directly in the Graphviz GUI. The structure itself was somewhat confusing, too; the Dot class never [...]

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Bicycling for Collatz

22Feb07

Q: How many people with ADD does it take to change a lightbulb?
A: HEY! Let’s ride bikes!

module Bikes where

Graphviz is fun. Graphviz is fair. You may already have one. You may already be there:

data Arr a = a :-> a

Graphviz plots graphs from .DOT files consisting of remarkably simple syntax:

instance (Show a) => Show (Arr [...]

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The Gee-Whiz Monad (I)

19Feb07

[] is really the gee-whiz monad. Haskell code that prints *all the five-number combinations of integers in [-5..5]:

mapM (\x->[x+i | i<-[-5..5]]) [1..5]

No, really, try it. This has to qualify as the “most surprisingly long output” line of code in all of computer programming.

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