The main benefits offered by a programming language are not only what it allows us to do, but also what it prevents us from doing. This conflict makes it hard for a single language to fulfil all needs of a large software project.

Scripting emphasizes the construction of software using two different languages; a system? language for the hard parts and a scripting language for the soft parts. This mix allows the development of programs that combine the qualities of both languages, such as performance and flexibility. Scripting is hardly a new idea; nevertheless, few languages have been designed with real scripting in mind.

Unlike most other dynamic languages, Lua is a language that has been designed from inception to be used as a scripting language. It is the leading scripting language in games. It is also widely used in embedded systems such as set-top boxes, routers, telecom equipment, and mobiles.

In this talk we will cover the most distinguishing features of Lua, emphasizing its trade-offs as a scripting language, the prominence of simplicity and small size in its design, and its use of a few simple but powerful concepts as unifying mechanisms.

Roberto Ierusalimschy is an Associate Professor of Informatics at PUC-Rio, where he works with programming-language design and implementation. Roberto is also the main designer of the Lua programming language. In 2013 he received the Scientific Merit Award from the Brazilian Computer Society (SBC). Roberto is a Senior Speaker from SBC, a Distinguished Speaker from ACM, and member of the IFIP Working Group on Language Design (IFIP WG 2.16).