Special issue on functional pearls Editorial

You are holding a necklace in your hands, composed of no fewer than thirteen exquisite pearls. The pearls are from all over the world, selected for the finest quality, smoothness and lustre. For your viewing pleasure, the necklace emphasizes variety, stringing pearls of wildly different color, shape and size. Satisfaction is guaranteed. This special issue of the Journal of Functional Programming is devoted to Functional Pearls. The original call for papers solicited articles that were small, rounded and enjoyable to read. Thirty-seven papers were submitted in response to the call, of which thirteen were finally selected for inclusion in this special issue. The pearls cover a diverse range of topics, including circuit design, coalgebra, combinator libraries, data compression, fractal geometry, ICFP programming contests, puzzles, spicery, type systems, and, of course, parsing. In nature, a masterpiece of a pearl is born from pain and suffering of the mother oyster. I do not know about the pain and suffering of the authors but the process of stringing this necklace was a very enjoyable one, due to the quality of papers and due to the overwhelming editorial support. More than a hundred referees helped to bring this special issue to life, in fact, too many to be listed here. Thank you! I would like to record a particular debt of gratitude to Richard Bird, the editor of JFP’s regular Functional Pearls column, for contributing two lovely pearls and for reviewing many more. Furthermore, special thanks go to Simon Peyton Jones and Phil Wadler for the opportunity to publish the pearls as a special issue of the Journal of Functional Programming.