Clean (programming language)

Clean is a general-purpose, purely functional programming language. For much of its active development it was known as Concurrent Clean, a name that was later dropped. The Programming Language Database dates it to 1987 and records its early development at Radboud University Nijmegen in the Netherlands. The database lists Miranda, Haskell, Prolog and C among its related languages, which reflects its place among lazy functional languages. Clean programs are organised into modules, and the sample code on the database page shows explicit type signatures such as square :: Int -> Int and a Start rule that serves as the entry point of a program. Its keywords include generic, derive, class, instance, where and with. Syntax highlighting for Clean is available in Pygments and on GitHub, and the language appears in the TIOBE Index.