Free monads, generic programming, fix-points and coproducts of data types are usually considered advanced topics for a Haskell programmer. In this talk we will look at these concepts from an unifying lens: combining and enriching pattern functors. A pattern functor is the stripped-down description of a data type: only the shape of the constructors remain, but all the recursive structure is gone. Using Haskell, we can manipulate pattern functors to create new data types at will.

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