Cours Lua: The evolution of Lua

Extrait du cours the evolution of Lua

Abstract
We report on the birth and evolution of Lua and discuss how it moved from a simple configuration language to a versatile widely used language that supports extensible semantics anonymous functions, full lexical scoping, proper tail calls and coroutines.
Categories and Subject Descriptors K.2 [HISTORY OF COMPUTING]: Software; D.3 [PROGRAMMING LAN- GUAGES]
1. Introduction
Lua is a scripting language born in 1993 at PUC-Rio, the Pontifical Catholic University of Rio de Janeiro in Brazil Since then, Lua has evolved to become widely used in all kinds of industrial applications, such as robotics, literate programming, distributed business, image processing, exten-
sible text editors, Ethernet switches, bioinformatics, finite-element packages, web development, and more [2]. In par-ticular, Lua is one of the leading scripting languages in game development.
2. Overview
In this section we give a brief overview of the Lua language and introduce the concepts discussed in §5 and §6. For a complete definition of Lua, see its reference manual [32].
For a detailed introduction to Lua, see Roberto’s book [28].For concreteness, we shall describe Lua 5.1, which is the current version at the time of this writing (April 2007), but most of this section applies unchanged to previous versions.
Semantically, Lua has many similarities with Scheme,even though these similarities are not immediately clear be-cause the two languages are syntactically very different. The influence of Scheme on Lua has gradually increased during Lua’s evolution: initially, Scheme was just a language in the background, but later it became increasingly important as a source of inspiration, especially with the introduction of anonymous functions and full lexical scoping.
3.2 SOL
At about the same time that DEL was created, a team lead by Roberto Ierusalimschy and Waldemar Celes started working on PGM, a configurable report generator for lithology pro- files, also for Petrobras. The reports generated by PGM con- sisted of several columns (called “tracks”) and were highly configurable: users could create and position the tracks, and could choose colors, fonts, and labels; each track could have a grid, which also had its set of options (log/linear, verti- cal and horizontal ticks, etc.); each curve had its own scale,which had to be changed automatically in case of overflow;etc. All this configuration was to be done by the end-users,typically geologists and engineers from Petrobras working in oil plants and off-shore platforms. The configurations had to be stored in files, for reuse. The team decided that the best way to configure PGM was through a specialized description language called SOL, an acronym for Simple Object Language.
4. Birth
The SOL team finished an initial implementation of SOL in March 1993, but they never delivered it. PGM would soon require support for procedural programming to allow the creation of more sophisticated layouts, and SOL would have to be extended. At the same time, as mentioned before, ED users had requested more power from DEL. ED also needed further descriptive facilities for programming its user interface. Around mid-1993, Roberto, Luiz Henrique, and Waldemar got together to discuss DEL and SOL, and con-cluded that the two languages could be replaced by a single, more powerful language, which they decided to design and implement. Thus the Lua team was born; it has not changed since.