This is your brain on Haskell

For the last week or so I’ve been playing a little with Haskell, which seems to be great fun. At pretty low intensity, that is, in the evenings. I’ve never done anything with functional programming before, though I’ve taken courses that involved a little recursion, a bit of algorithms etc, so everything is not completely foreign to me. Well, it feels very foreign, a bit like trying to read French (I don’t read French).

Anyway, I felt like it was time to write a little program that actually does something, so I’ll try to make a script for bootstrapping. Even though bootstrapping is not the best thing in the world, a bootstrap comparison between the means of two groups seems a nice task to try: it is not completely trivial, but will make me try useful things like pseudorandom numbers and reading a csv file.

Of course, I haven’t got that far yet. Here is the script on github. (Yes, I’m also trying to get used to github.) When trying to do anything I quickly find myself thinking in terms of procedures, states and side-effects, or otherwise thinking wrong. On the other hand, yesterday evening just before sleep, I had one of those code epiphanies. ”Of course, I just need to do that . . . ” So, while the half-baked script is not that impressive, the process of writing it is probably the most fun I’ve had with a computer since Starcraft II: Wings of Liberty.

Right now, it can make bootstrap replicates of a list of integers, using a sequence of pseudorandom numbers (derived from the seed 42, so not random at all, but I’m sure you can get entropy through some monad later). I think the next thing will something to get data into the script.

I’m just remembering how to do recursion. Like this little thing, that puts data in some given order. It just handles the first element, then calls itself to deal with the rest. I think this is why I like the apply-split-combine approach in R so much, because it really feels like you’re doing almost no work at all.

applyShuffle x shuffle =
  if shuffle == [] then
    []
  else
    [x !! head shuffle] ++ applyShuffle x (tail shuffle)

To be continued, I guess.

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