This paper describes Lua, a language for extending applications. Lua combines procedural features with powerful data description facilities, by using a simple, yet powerful, mechanism of tables. This mechanism implements the concepts of records, arrays, and recursive data types (pointers), and adds some object-oriented facilities, such as methods with dynamic dispatching. Lua presents a mechanism of fallbacks that allows programmers to extend the semantics of the language in some unconventional ways. As a noteworthy example, fallbacks allow the user to add different kinds of inheritance to the language. Currently, Lua is being extensively used in production for several tasks, including user configuration, general-purpose data-entry, description of user interfaces, storage of structured graphical metafiles, and generic attribute configuration for finite element meshes.

We describe the design and the implementation of Lua, a simple, yet powerful, language for extending applications. Although Lua is a procedural language, it has data description facilities, and has been extensively used in production for several tasks including user configuration, general-purpose data-entry, description of user interfaces, description of application objects, and storage of structured graphical metafiles.

Abstract This paper proposes the investigation of the role of interpreted languages as a tool for the development of parallel programs in distributed environments. Besides, it argues that an event-driven approach simplifies many aspects of concurrent programming, since processes are never blocked on communication primitives. These ideas were experimented with through the implementation of several solutions to the classical problem of termination detection. This implementation has used a programming environment based on the extension language Lua.