Lua is a programming language originally designed for extending applications, but also frequently used as a general-purpose, stand-alone language. Lua combines simple procedural syntax (similar to Pascal) with powerful data description constructs based on associative arrays and extensible semantics. Lua is dynamically typed, interpreted from bytecodes, and has automatic memory management with garbage collection, making it ideal for configuration, scripting, and rapid prototyping. A fundamental concept in the design of Lua is to provide meta-mechanisms for implementing features, instead of providing a host of features directly in the language. For example, although Lua is not a pure object-oriented language, it does provide meta-mechanisms for implementing classes and inheritance. Lua's meta-mechanisms bring an economy of concepts and keep the language small, while allowing the semantics to be extended in unconventional ways. Extensible semantics is a distinguishing feature of Lua. Lua is implemented as a small library of C functions, written in ANSI C, and compiles unmodified in all known platforms. The implementation goals are simplicity, efficiency, portability, and low embedding cost. WWW: http://www.tecgraf.puc-rio.br/lua/