Lennart Augustsson functional programming relic left over from the heydays of declarative programming, i.e., the 1980s. In addition to one of the first Haskell compilers, hbc, Lennart has also tried to get functional programming into hardware design, Bluespec, and banking, Mu.
Lennart is so bad at imperative programming that his code has gotten prizes at the International Obfuscated C Code Contest.
Orthotope is a Haskell library for multi-dimensional arrays, with an API is somewhat inspired by APL. The library provides a number of efficient structural (i.e., changing the shape of the array, but not its contents) operations on arrays. By using a clever (and ancient) representation of arrays, many structural operations can be done in constant time. The array comes in several variants depending on what underlying storage is used, and how strongly typed the API is.