Lambda the Ultimate

Link: This article gives an easy to follow introduction to the SETL language. SETL has been around since 1970 and excels at manipulating sets.

Being a mathematician, I've always dreamt of a programming language that would make use of the powerful formalism of Set Theory. Two years ago, I started looking for an open-source software tool to use in an elementary Set Theory class. I had a hard time finding any on the Net, but in the end I found the object of my dreams: a structured, general-purpose, open-source programming language that implements as closely as possible the Set Theory formal language.

(Previous LtU discussion)