Saturday, March 17, 2007


I was getting mighty sick of socket programming, so I did what any good programmer does. Procrastinate by surfing the web. I happened upon's collection of solutions to the Ruby quiz puzzles, in Haskell. The random page function is neato. I took a stab at the first one, Bruce Schneier's solitaire cypher.

I spent a lot of time reading up on list manipulation functions in Data.List. That library is awesome. I didn't really grok the utility of zipWith until I caught myself thinking, I have two lists i would like to combine. Another function I put to good use was groupBy. groupBy is sort of odd, but i think there's a fair amount of utility there. I couldn't' think of a clever way to break a list up into a list of lists of 5 elements. it's *almost* like map, but needs to look at more of the list. I suppose there's something like reverse $ foldl (\acc val -> if (length head acc < 5) then (val:(head acc)):(tail acc) else [val]:acc but that seems opaque.

I ran into a couple of problems, I need to learn to read specifications very carefully. I wasted a fair amount of time by missing the part that both Jokers are considered 53 when used in a numeric context, I had used one Joker as 53 and another as 54. There were also some fiddly little details with converting from numeric to ascii codes... off by one error essentially.

Anyway, check out the quizzes. they're nice sized problems. Challenging enough to be more than a toy, but not so large that they're daunting. Keep a window on the haskell libraries open too. There's great stuff in the library you'll never realize you need till you're in the thick of a problem. Well, it worked well for me anyway.

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