Arc (programming language)

Arc is a dialect of the Lisp programming language, created in 2001 by Paul Graham and Robert Morris. Like other Lisp family languages it is written in S-expressions, and the Programming Language Database lists a wide circle of related languages including Lisp, Scheme, Racket, Common Lisp and Clojure. Macros are a central feature: a macro is defined much like a function but with mac in place of def, and it generates code that replaces the macro call before evaluation. Output is printed with prn, so the traditional greeting program is a single line, and the example code shown on the page includes a small web form handler. The community around it is small, with a few hundred public repositories on GitHub, and another language, Bel, links back to it.