Eric Normand:

Rich Hickey explained the design choices behind Clojure and made many statements about static typing along the way. I share an interesting perspective and some stories from my time as a Haskell programmer. I conclude with a design challenge for the statically typed world.

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People often talk about a Person class representing a person. But it doesn’t. It represents information about a person. A Person type, with certain fields of given types, is a concrete choice about what information you want to keep out of all of the possible choices of what information to track about a person. An abstraction would ignore the particulars and let you store any information about a person. And while you’re at it, it might as well let you store information about anything. There’s something deeper there, which is about having a higher-order notion of data.