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!