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We have two meaty articles in PragPub this month, plus some tasty side dishes.

Paul Callaghan returns with another article on the Haskell language. According to Wikipedia, “The language is rooted in the observations of Haskell Curry and his intellectual descendants, that ‘a proof is a program; the formula it proves is a type for the program.’” Paul shows you what that means in this deep but engaging article. He shows you how Haskell deals with types, but he goes beyond that to explore just how much sophisticated intellgence can be encoded in a type specification. And from there he goes on to the relationships among testing and types and proofs. It’s quite a ride.

Alexander Demin has appeared in our pages before, with an article on concurrency in Google’s Go language in June and an article on building a CPU with only one instruction in March. He’s back this month with something a little more conventional: a step-by-step walkthrough on writing an app for the iPhone. What makes it a little different is that although Alexander is an experienced developer, he had never before written iOS app, or even written anything in Objective-C. So the article is also about a developer trying out a new language and environment and sharing his experience by sharing his code. We think this kind of article can be educational in a slightly different way from the platform expert showing how it’s done. Let us know what you think.

Meanwhile, Mike Nygard tells another story of his adventures trying to keep large websites up and running. This time it’s a site that went down every morning at 5 A.M. Your editor has another glimpse into personal computer history, with three snapshots from the life of Chris Espinosa, who has been at Apple all of its life and most of his own.

And John Shade weighs in on the Apple-Samsung lawsuit decision.