17 January 2007

Haskell Books Piling Up, and Herpes Zoster Ophthalmicus at One Month

I've received a couple of Haskell-related books -- my Christmas presents to myself. I have only been able to skim these books, but here are my first impressions.

The first book is Chris Okasaki's Purely Functional Data Structures. When I was working on some code to solve Sudoku puzzles in Scheme, I became stymied because in the midst of my efforts to program in a function style, I kept slipping back into an imperative style. This book is the answer to the question "how do you manage data structures when you don't have mutable variables?" The answer, of course, is that you return new data structures based on the old ones. This is not necessarily as inefficient as you might expect, because the new data structure can frequently share content -- sometimes most of the content -- with the previous data structure. Okasaki's book is a model of clarity; on the back it indicates that it can be used for self-study. A lot of texts claim that, but this book seems to actually deliver it. The diagrams are marvelously clear and the learning curve is gentle. The body of the text uses Standard ML with extensions but there is an appendix containing Haskell code. I will have more to say about this book in future postings; I am really looking forward to trying out some of the ideas it contains.

The second book is The Haskell Road to Logic, Maths, and Programming by Kees Doets and Jan van Eijck. This is part of the King's College Texts in Computing series which includes An Introduction to Lambda Calculi for Computer Scientists. That book is thin, while this one is fairly fat; this volume is bursting with exposition (and code) on logic, set theory, and other topics dear to my heart. It looks quite fascinating and again I hope to have more to say about it soon.

It has been approximately a month since I was hit with the first symptoms of herpes zoster ophthalmicus (shingles infection involving the eye). The news is generally very good: there is little long-term damage to my cornea. My opthalmologist can see some slight scarring, but it should continue to improve. But the pain and hyper-sensitivity to light has persisted, and I have found it difficult to return to work because my eye tends to start watering madly or lose focus when I work at the computer for longer than a few minutes. The problem is in the branches of the trigeminal nerve, not the eyeball itself. Nerves heal slowly, so this is unfortunately not an illness for the impatient!

02 January 2007


Well, I had great plans for my ten days off -- work on the apartment, organize the office, deep-clean the kitchen, read, and study Haskell!

So much for best-laid plans. Just before Christmas I came down with a shingles infection, which started in my right eye.

Shingles is a reactivation of the herpes zoster or "varicella" virus, the same virus that causes chicken pox. I did a near all-nighter the Monday a week before Christmas, which might not have been too bad, but then the following night we had a sick baby and I was also unable to sleep. That was apparently enough stress to cause the virus to reactivate.

Shingles is painful. I have become intimately familiar with two new types of pain, which I call the blowtorch and the nightstick. The blowtorch is a feeling like my skin is being burned by an open flame and is bubbling. That is the sensation of the blisters forming, although it comes at other random times too. The nightstick is deep pain along the nerves of my face, where they feel like I've been beaten. That produces a tremendous amount of muscle tension in my jaw, and around the base of my skull as well, where large areas are still hyper-sensitive to touch.

Valtrex (an anti-retroviral drug) also has nasty side effects. I got waves of fever and chills, often back-to-back. It also caused nausea, diziness, and strange visions. I'm off the Valtrex now, so thankfully those side effects have gone away.

For most of my ten days off work I was fairly incapacitated: unable to see, unable to read, lying in bed with fever or chills and with strange pains, covered with blisters and scabs. When I got out of bed, I was dizzy, stumbling around the house looking like a crazed sunburned pirate with an eye-patch on.

Anyway, I am now back at work. The scabs are gone, although my face is still visibly splotchy. My right eye is still swollen and there is still some pain. I am still using an antibiotic gel in my eye, which means my right eye is still hazy, so I am not driving yet. I see my regular doctor today and the ophthalmologist again tomorrow. I think the likely outcome is that my vision will not be significantly damaged. It seems like the pain will persist at reduced level for at least a while longer.

Dear reader, I sincerely hope you had a better holiday than mine. And if not, God bless you!