Einar Høst

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Einar W. Høst is a computer at NRK, the Norwegian public broadcaster. He thinks that programs should be written for people to read and also for machines to laugh at. He has a PhD in Computer Science from the University of Oslo.

Composition by Juxtaposition: A PostScript on Functional Geometry

Peter Henderson's "Functional Geometry" is a classic paper that shows the beauty and power of functional abstraction and composition. Using functions to represent pictures, Henderson defines a small set of combinators to create a replica of Escher's recursive tessellation "Square Limit". It's a nice kata for functional programmers, with straightforward implementations in the ML family of programming languages. However, you could also implement Henderson's combinators effectively and elegantly in concatenative languages, where composition is nothing more than juxtaposition. In this talk, we'll look at an implementation in PostScript, a proven and battle-worn concatenative language that has been on the plateau of productivity for decades. It also happens to be rather good for drawing.

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