From 69b45bb4e9b08469e9fe2148d0aebf49ec54c6d2 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Fri, 12 May 2000 16:19:18 -0300
Subject: changes by lhf

---
 manual.tex | 1848 +++++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 1092 insertions(+), 756 deletions(-)

(limited to 'manual.tex')

diff --git a/manual.tex b/manual.tex
index 3784b4ea..7d0494e9 100644
--- a/manual.tex
+++ b/manual.tex
@@ -1,21 +1,23 @@
-% $Id: manual.tex,v 1.35 2000/04/14 17:47:55 roberto Exp roberto $
+% $Id: manual.tex,v 1.36 2000/04/17 19:23:48 roberto Exp roberto $
 
 \documentclass[11pt]{article}
 \usepackage{fullpage,bnf}
+\usepackage{graphicx}
+%\usepackage{times}
 
 \catcode`\_=12
 
 \newcommand{\See}[1]{Section~\ref{#1}}
 \newcommand{\see}[1]{(see \See{#1})}
-\newcommand{\M}[1]{\emph{#1}}
+\newcommand{\M}[1]{\rm\emph{#1}}
 \newcommand{\T}[1]{{\tt #1}}
 \newcommand{\Math}[1]{$#1$}
 \newcommand{\nil}{{\bf nil}}
-\newcommand{\Line}{\rule{\linewidth}{.5mm}}
 \def\tecgraf{{\sf TeC\kern-.21em\lower.7ex\hbox{Graf}}}
 
 \newcommand{\Index}[1]{#1\index{#1}}
 \newcommand{\IndexVerb}[1]{\T{#1}\index{#1}}
+\newcommand{\IndexEmph}[1]{\emph{#1}\index{#1}}
 \newcommand{\Def}[1]{\emph{#1}\index{#1}}
 \newcommand{\Deffunc}[1]{\index{#1}}
 
@@ -23,75 +25,46 @@
 
 \newcommand{\Version}{4.0}
 
+% LHF
+\renewcommand{\ter}[1]{{\rm`{\tt#1}'}}
+\newcommand{\NOTE}{\par\noindent\emph{NOTE}: }
+
 \makeindex
 
 \begin{document}
 
-\title{Reference Manual of the Programming Language Lua \Version}
-
-\author{%
-Roberto Ierusalimschy\quad
-Luiz Henrique de Figueiredo\quad
-Waldemar Celes
-\vspace{1.0ex}\\
-\smallskip
-\small\tt lua@tecgraf.puc-rio.br
-\vspace{2.0ex}\\
-%MCC 08/95 ---
-\tecgraf\ --- Computer Science Department --- PUC-Rio
-}
-
-\date{{\small \tt\$Date: 2000/04/14 17:47:55 $ $}}
-
-\maketitle
-
+%{===============================================================
 \thispagestyle{empty}
 \pagestyle{empty}
 
-\begin{abstract}
-\noindent
-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 opcodes,
-and has automatic memory management with garbage collection,
-making it ideal for configuration, scripting, and rapid prototyping.
-
-This document describes version \Version\ of the Lua programming language
-and the API that allows interaction between Lua programs and their
-host C programs.
-\end{abstract}
-\vspace{4ex}
-\begin{quotation}
-\small
-\begin{center}{\bf Sum\'ario}\end{center}
-\vspace{1ex}
-\noindent
-Lua \'e uma linguagem de programa\c{c}\~ao originalmente projetada para
-extens\~ao de aplica\c{c}\~oes,
-e que \'e tamb\'em frequentemente usada como uma linguagem de
-prop\'osito geral.
-Lua combina uma sintaxe procedural simples (similar a Pascal)
-com poderosas facilidades para descri\c{c}\~ao de dados baseadas
-em tabelas associativas e uma sem\^antica estens\'{\i}vel.
-Lua tem tipagem din\^amica, \'e interpretada via opcodes,
-e tem gerenciamento autom\'atico de mem\'oria com coleta de lixo,
-tornando-se ideal para configura\c{c}\~ao, scripting,
-e prototipagem r\'apida.
-
-Este documento descreve a vers\~ao \Version\ da linguagem de
-programa\c{c}\~ao Lua e a Interface de Programa\c{c}\~ao (API) que permite
-a intera\c{c}\~ao entre programas Lua e programas C hospedeiros.
-\end{quotation}
-
+{
+\parindent=0pt
+\vglue1.5in
+{\LARGE\bf
+The Programming Language Lua}
+\hfill
+\vskip4pt \hrule height 4pt width \hsize \vskip4pt
+\hfill
+Reference Manual for Lua version \Version
+\\
+\null
+\hfill
+Last revised on \today
+\\
+\vfill
+\centering
+\includegraphics[width=0.7\textwidth]{nolabel.ps}
+\vfill
+\vskip4pt \hrule height 2pt width \hsize
+}
 
 \newpage
 \begin{quotation}
 \parskip=10pt
-\noindent
 \footnotesize
+\null\vfill
+
+\noindent
 Copyright \copyright\ 1994--2000 TeCGraf, PUC-Rio.  All rights reserved.
 
 \noindent
@@ -127,10 +100,89 @@ Figueiredo at TeCGraf, PUC-Rio.
 
 \noindent
 This implementation contains no third-party code.
-\end{quotation}
 
+\noindent
+Copies of this manual can be obtained at
+\verb|http://www.tecgraf.puc-rio.br/lua/|.
+\end{quotation}
+%}===============================================================
 \newpage
 
+\title{Reference Manual of the Programming Language Lua \Version}
+
+\author{%
+Roberto Ierusalimschy\quad
+Luiz Henrique de Figueiredo\quad
+Waldemar Celes
+\vspace{1.0ex}\\
+\smallskip
+\small\tt lua@tecgraf.puc-rio.br
+\vspace{2.0ex}\\
+%MCC 08/95 ---
+\tecgraf\ --- Computer Science Department --- PUC-Rio
+}
+
+\date{{\small \tt\$Date: 2000/04/17 19:23:48 $ $}}
+
+\maketitle
+
+\thispagestyle{empty}
+\pagestyle{empty}
+
+\begin{abstract}
+\noindent
+Lua is a powerful, light-weight programming language
+designed for extending applications.
+Lua is 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.
+
+This document describes version \Version\ of the Lua programming language
+and the API that allows interaction between Lua programs and their
+host C programs.
+\end{abstract}
+
+\def\abstractname{Resumo}
+\begin{abstract}
+\noindent
+Lua \'e uma linguagem de programa\c{c}\~ao
+poderosa e leve,
+projetada para extender aplica\c{c}\~oes.
+Lua tamb\'em \'e frequentemente usada como uma linguagem de prop\'osito geral.
+Lua combina programa\c{c}\~ao procedural
+(com sintaxe semelhante \`a de Pascal)
+com
+poderosas constru\c{c}\~oes para descri\c{c}\~ao de dados,
+baseadas em tabelas associativas e sem\^antica extens\'\i vel.
+Lua \'e
+tipada dinamicamente,
+interpretada a partir de \emph{bytecodes},
+e tem gerenciamento autom\'atico de mem\'oria com coleta de lixo.
+Essas caracter\'{\i}sticas fazem de Lua uma linguagem ideal para
+configura\c{c}\~ao,
+automa\c{c}\~ao (\emph{scripting})
+e prototipagem r\'apida.
+
+Este documento descreve a vers\~ao \Version\ da linguagem de
+programa\c{c}\~ao Lua e a Interface de Programa\c{c}\~ao (API) que permite
+a intera\c{c}\~ao entre programas Lua e programas C hospedeiros.
+\end{abstract}
+
+\newpage
+\null
+\newpage
 \tableofcontents
 
 \newpage
@@ -143,7 +195,7 @@ This implementation contains no third-party code.
 Lua is an extension programming language designed to support
 general procedural programming with data description
 facilities.
-Lua is intended to be used as a light-weight, but powerful,
+Lua is intended to be used as a powerful, light-weight
 configuration language for any program that needs one.
 
 Lua is implemented as a library, written in C.
@@ -152,8 +204,8 @@ it only works \emph{embedded} in a host client,
 called the \emph{embedding} program.
 This host program can invoke functions to execute a piece of
 code in Lua, can write and read Lua variables,
-and can register C functions to be called by Lua code.
-Through the use of C functions, Lua can be augmented to cope with
+and can register C~functions to be called by Lua code.
+Through the use of C~functions, Lua can be augmented to cope with
 a wide range of different domains,
 thus creating customized programming languages sharing a syntactical framework.
 
@@ -164,9 +216,28 @@ The implementation described in this manual is available
 at the following URL's:
 \begin{verbatim}
    http://www.tecgraf.puc-rio.br/lua/
-   ftp://ftp.tecgraf.puc-rio.br/pub/lua/lua.tar.gz
+   ftp://ftp.tecgraf.puc-rio.br/pub/lua/
 \end{verbatim}
 
+Like any other reference manual,
+this document is dry in places.
+For a discussion of the decisions behind the design of Lua,
+see the papers below,
+which are available at the web site above.
+\begin{itemize}
+\item
+R.~Ierusalimschy, L.~H.~de Figueiredo, and W.~Celes.
+Lua---an extensible extension language.
+\emph{Software: Practice \& Experience} {\bf 26} \#6 (1996) 635--652.
+\item
+L.~H.~de Figueiredo, R.~Ierusalimschy, and W.~Celes.
+The design and implementation of a language for extending applications.
+\emph{Proceedings of XXI Brazilian Seminar on Software and Hardware} (1994) 273--283.
+\item
+L.~H.~de Figueiredo, R.~Ierusalimschy, and W.~Celes.
+Lua: an extensible embedded language.
+\emph{Dr. Dobb's Journal} {\bf  21} \#12 (Dec 1996) 26--33.
+\end{itemize}
 
 \section{Environment and Chunks}
 
@@ -177,7 +248,7 @@ is initialized with a call from the embedding program to
 persists until a call to \verb|lua_close|,
 or the end of the embedding program.
 Optionally, a user can create multiple independent global
-environments \see{mangstate}.
+environments, and freely switch between them \see{mangstate}.
 
 The global environment can be manipulated by Lua code or
 by the embedding program,
@@ -196,16 +267,18 @@ A chunk is simply a sequence of statements:
 \produc{chunk}{\rep{stat} \opt{ret}}
 \end{Produc}%
 Statements are described in \See{stats}.
-(As usual, \rep{\emph{a}} means 0 or more \emph{a}'s,
-\opt{\emph{a}} means an optional \emph{a} and \oneormore{\emph{a}} means
-one or more \emph{a}'s.)
+(The notation above is the usual extended BNF,
+in which
+\rep{\emph{a}} means 0 or more \emph{a}'s,
+\opt{\emph{a}} means an optional \emph{a}, and
+\oneormore{\emph{a}} means one or more \emph{a}'s.)
 
 A chunk may be in a file or in a string inside the host program.
 A chunk may optionally end with a \verb|return| statement \see{return}.
 When a chunk is executed, first all its code is pre-compiled,
-then the statements are executed in sequential order.
+and then the statements are executed in sequential order.
 All modifications a chunk effects on the global environment persist
-after the chunk end.
+after the chunk ends.
 
 Chunks may also be pre-compiled into binary form;
 see program \IndexVerb{luac} for details.
@@ -216,11 +289,12 @@ Lua automatically detects the file type and acts accordingly.
 
 \section{\Index{Types and Tags}} \label{TypesSec}
 
-Lua is a dynamically typed language.
-Variables do not have types; only values do.
+Lua is a \emph{dynamically typed language}.
+This means that
+variables do not have types; only values do.
 Therefore, there are no type definitions in the language.
 All values carry their own type.
-Besides a type, all values also have a \Index{tag}.
+Besides a type, all values also have a \IndexEmph{tag}.
 
 There are six \Index{basic types} in Lua: \Def{nil}, \Def{number},
 \Def{string}, \Def{function}, \Def{userdata}, and \Def{table}.
@@ -230,18 +304,18 @@ whose main property is to be different from any other value.
 while \emph{string} has the usual meaning.
 Lua is \Index{eight-bit clean},
 and so strings may contain any 8-bit character,
-\emph{including} embedded zeros (\verb|'\0'|).
+\emph{including} embedded zeros (\verb|'\0'|) \see{lexical}.
 The \verb|type| function returns a string describing the type
 of a given value \see{pdf-type}.
 
-Functions are considered first-class values in Lua.
+Functions are considered \emph{first-class values} in Lua.
 This means that functions can be stored in variables,
 passed as arguments to other functions, and returned as results.
 Lua can call (and manipulate) functions written in Lua and
 functions written in C.
-They can be distinguished by their tags:
+The kinds of functions can be distinguished by their tags:
 all Lua functions have the same tag,
-and all C functions have the same tag,
+and all C~functions have the same tag,
 which is different from the tag of Lua functions.
 The \verb|tag| function returns the tag
 of a given value \see{pdf-tag}.
@@ -263,7 +337,7 @@ Tables are the main data structuring mechanism in Lua.
 To represent \Index{records}, Lua uses the field name as an index.
 The language supports this representation by
 providing \verb|a.name| as syntactic sugar for \verb|a["name"]|.
-Tables may also carry methods:
+Tables may also carry \emph{methods}:
 Because functions are first class values,
 table fields may contain functions.
 The form \verb|t:f(x)| is syntactic sugar for \verb|t.f(t,x)|,
@@ -281,10 +355,10 @@ Tags are mainly used to select \emph{tag methods} when
 some events occur.
 Tag methods are the main mechanism for extending the
 semantics of Lua \see{tag-method}.
-Each of the types \M{nil}, \M{number} and \M{string} has a different tag.
-All values of each of these types have this same pre-defined tag.
+Each of the types \M{nil}, \M{number}, and \M{string} has a different tag.
+All values of each of these types have the same pre-defined tag.
 Values of type \M{function} can have two different tags,
-depending on whether they are Lua functions or C functions.
+depending on whether they are Lua functions or C~functions.
 Finally,
 values of type \M{userdata} and \M{table} have
 variable tags, assigned by the program \see{tag-method}.
@@ -296,40 +370,42 @@ there is the function \verb|settag| \see{pdf-newtag}.
 
 \section{The Language}
 
-This section describes the lexis, the syntax and the semantics of Lua.
+This section describes the lexis, the syntax, and the semantics of Lua.
 
 
 \subsection{Lexical Conventions} \label{lexical}
 
-\Index{Identifiers} in Lua can be any string of letters,
+\IndexEmph{Identifiers} in Lua can be any string of letters,
 digits, and underscores,
 not beginning with a digit.
-The definition of letter depends on the current locale:
+This coincides with the definition of identifiers in most languages,
+except that
+the definition of letter depends on the current locale:
 Any character considered alphabetic by the current locale
 can be used in an identifier.
-The following words are reserved, and cannot be used as identifiers:
+The following words are \emph{reserved}, and cannot be used as identifiers:
 \index{reserved words}
 \begin{verbatim}
-      and       break     do        else
-      elseif    end       for       function
-      if        local     nil       not
-      or        repeat    return    then
-      until     while
+   and       break     do        else
+   elseif    end       for       function
+   if        local     nil       not
+   or        repeat    return    then
+   until     while
 \end{verbatim}
 Lua is a case-sensitive language:
 \T{and} is a reserved word, but \T{And} and \T{\'and}
-(if the locale permits) are two other different identifiers.
+(if the locale permits) are two different, valid identifiers.
 As a convention, identifiers starting with underscore followed by
 uppercase letters (such as \verb|_INPUT|)
 are reserved for internal variables.
 
 The following strings denote other \Index{tokens}:
 \begin{verbatim}
-         ~=  <=  >=  <   >   ==  =   +   -   *   /   %
-         (   )   {   }   [   ]   ;   ,   .   ..  ...
+   ~=  <=  >=  <   >   ==  =   +   -   *   /   %
+   (   )   {   }   [   ]   ;   ,   .   ..  ...
 \end{verbatim}
 
-\Index{Literal strings} can be delimited by matching single or double quotes,
+\IndexEmph{Literal strings} can be delimited by matching single or double quotes,
 and can contain the C-like escape sequences
 \verb|'\a'| (bell),
 \verb|'\b'| (backspace),
@@ -341,14 +417,15 @@ and can contain the C-like escape sequences
 \verb|'\\'|, (backslash),
 \verb|'\"'|, (double quote),
 \verb|'\''| (single quote),
-and \verb|'\\n'| (that is, a backslash followed by a real newline,
+and \verb|'\|\emph{newline}\verb|'| (that is, a backslash followed by a real newline,
 which  results in a newline in the string).
 A character in a string may also be specified by its numerical value,
 through the escape sequence \verb|'\ddd'|,
 where \verb|ddd| is a sequence of up to three \emph{decimal} digits.
-Strings in Lua may contain any 8-bit value, including embedded zeros.
+Strings in Lua may contain any 8-bit value, including embedded zeros,
+which can be specified as \verb|'\000'|.
 
-Literal strings can also be delimited by matching \verb|[[ ... ]]|.
+Literal strings can also be delimited by matching \verb|[[| \dots\ \verb|]]|.
 Literals in this bracketed form may run for several lines,
 may contain nested \verb|[[ ... ]]| pairs,
 and do not interpret escape sequences.
@@ -376,29 +453,30 @@ in Unix systems \see{lua-sa}.
 and an optional decimal exponent.
 Examples of valid numerical constants are
 \begin{verbatim}
-       3     3.0     3.1416  314.16e-2   0.31416E1
+   3     3.0     3.1416  314.16e-2   0.31416E1
 \end{verbatim}
 
 \subsection{The \Index{Pre-processor}} \label{pre-processor}
 
 All lines that start with a \verb|$| sign are handled by a pre-processor.
-The \verb|$| sign must be immediately
-followed by one of the following directives:
+The following directives are understood by the pre-processor:
 \begin{description}
-\item[\T{debug}] --- turn on debugging facilities \see{pragma}.
-\item[\T{nodebug}] --- turn off debugging facilities \see{pragma}.
-\item[\T{if \M{cond}}] --- starts a conditional part.
+\item[\T{\$debug}] --- turn on debugging facilities \see{pragma}.
+\item[\T{\$nodebug}] --- turn off debugging facilities \see{pragma}.
+\item[\T{\$if \M{cond}}] --- start a conditional part.
 If \M{cond} is false, then this part is skipped by the lexical analyzer.
-\item[\T{ifnot \M{cond}}] --- starts a conditional part.
+\item[\T{\$ifnot \M{cond}}] --- start a conditional part.
 If \M{cond} is true, then this part is skipped by the lexical analyzer.
-\item[\T{end}] --- ends a conditional part.
-\item[\T{else}] --- starts an ``else'' conditional part,
+\item[\T{\$end}] --- end a conditional part.
+\item[\T{\$else}] --- start an ``else'' conditional part,
 flipping the ``skip'' status.
-\item[\T{endinput}] --- ends the lexical parse of the file.
+\item[\T{\$endinput}] --- end the lexical parse of the chunk.
+For all purposes,
+it is as if the chunk physically ended at this point.
 \end{description}
 
 Directives may be freely nested.
-Particularly, a \verb|$endinput| may occur inside a \verb|$if|;
+In particular, a \verb|$endinput| may occur inside a \verb|$if|;
 in that case, even the matching \verb|$end| is not parsed.
 
 A \M{cond} part may be
@@ -418,6 +496,11 @@ Any arithmetic operation applied to a string tries to convert
 that string to a number, following the usual rules.
 Conversely, whenever a number is used when a string is expected,
 that number is converted to a string, in a reasonable format.
+The format is chosen so that
+a conversion from number to string then back to number
+reproduces the original number \emph{exactly}.
+Thus,
+the conversion does not necessarily produces nice-looking text for some numbers.
 For complete control on how numbers are converted to strings,
 use the \verb|format| function \see{format}.
 
@@ -427,15 +510,15 @@ use the \verb|format| function \see{format}.
 Functions in Lua can return many values.
 Because there are no type declarations,
 when a function is called
-the system does not know how many values a function will return,
+the system does not know how many values the function will return,
 or how many parameters it needs.
 Therefore, sometimes, a list of values must be \emph{adjusted}, at run time,
 to a given length.
 If there are more values than are needed,
 then the excess values are thrown away.
-If there are more needs than values,
+If there are less values than are needed,
 then the list is extended with as many  \nil's as needed.
-Adjustment occurs in multiple assignment \see{assignment}
+This adjustment occurs in multiple assignments \see{assignment}
 and function calls \see{functioncall}.
 
 
@@ -444,21 +527,22 @@ and function calls \see{functioncall}.
 Lua supports an almost conventional set of \Index{statements},
 similar to those in Pascal or C.
 The conventional commands include
-assignment, control structures and procedure calls.
+assignment, control structures, and procedure calls.
 Non-conventional commands include table constructors
-\see{tableconstructor},
+\see{tableconstructor}
 and local variable declarations \see{localvar}.
 
 \subsubsection{Blocks}
 A \Index{block} is a list of statements, which are executed sequentially.
-A statement may be have an optional label,
+A statement may be have an optional \Index{label},
+which is syntactically an identifier,
 and can be optionally followed by a semicolon:
 \begin{Produc}
-\produc{block}{\opt{label} \rep{stat sc}}
-\produc{sc}{\opt{\ter{;}}}
+\produc{block}{\opt{label} \rep{stat \opt{\ter{;}}}}
 \produc{label}{\ter{$\vert$} name \ter{$\vert$}}
 \end{Produc}%
-For syntactic reasons, \rwd{return} and
+\NOTE
+For syntactic reasons, the \rwd{return} and
 \rwd{break} statements can only be written
 as the last statement of a block.
 
@@ -467,7 +551,7 @@ A block may be explicitly delimited:
 \produc{stat}{\rwd{do} block \rwd{end}}
 \end{Produc}%
 This is useful to control the scope of local variables \see{localvar},
-and to add a \rwd{return} or a \rwd{break} statement in the middle
+and to add a \rwd{return} or \rwd{break} statement in the middle
 of another block:
 \begin{verbatim}
   do return end        -- return is the last statement in this block
@@ -476,7 +560,7 @@ of another block:
 \subsubsection{\Index{Assignment}} \label{assignment}
 The language allows \Index{multiple assignment}.
 Therefore, the syntax for assignment
-defines a list of variables on the left side,
+defines a list of variables on the left side
 and a list of expressions on the right side.
 Both lists have their elements separated by commas:
 \begin{Produc}
@@ -486,12 +570,20 @@ Both lists have their elements separated by commas:
 This statement first evaluates all values on the right side
 and eventual indices on the left side,
 and then makes the assignments.
-Therefore, it can be used to exchange two values, as in
+So
+\begin{verbatim}
+   i = 3
+   i, a[i] = 4, 20
+\end{verbatim}
+sets \verb|a[3]| to 20, but does not affect \verb|a[4]|.
+
+Multiple assignment can be used to exchange two values, as in
 \begin{verbatim}
    x, y = y, x
 \end{verbatim}
-The two lists may have different lengths.
-Before the assignment, the list of values is \emph{adjusted} to
+
+The two lists in a multiple assignment may have different lengths.
+Before the assignment, the list of values is adjusted to
 the length of the list of variables \see{adjust}.
 
 A single name can denote a global variable, a local variable,
@@ -504,7 +596,7 @@ Square brackets are used to index a table:
 \produc{var}{simpleexp \ter{[} exp1 \ter{]}}
 \end{Produc}%
 The \M{simpleexp} should result in a table value,
-from where the field indexed by the expression
+from where the field indexed by the expression \M{exp1}
 value gets the assigned value.
 
 The syntax \verb|var.NAME| is just syntactic sugar for
@@ -517,47 +609,50 @@ The meaning of assignments and evaluations of global variables and
 indexed variables can be changed by tag methods \see{tag-method}.
 Actually,
 an assignment \verb|x = val|, where \verb|x| is a global variable,
-is equivalent to a call \verb|setglobal('x', val)|;
+is equivalent to a call \verb|setglobal("x", val)|;
 an assignment \verb|t[i] = val| is equivalent to
-\verb|settable_event(t, i, val)|.
+\verb|settable_event(t,i,val)|.
 See \See{tag-method} for a complete description of these functions.
-(Function \verb|setglobal| is pre-defined in Lua.
-Function \T{settable\_event} is used only for explanatory purposes.)
+(The function \verb|setglobal| is pre-defined in Lua.
+The function \T{settable\_event} is used only for explanatory purposes.)
 
 \subsubsection{Control Structures}
-The \Index{condition expression} of a control structure may return any value.
-All values different from \nil\ are considered true;
-only \nil\ is considered false.
-\T{if}'s, \T{while}'s and \T{repeat}'s have the usual meaning.
-
-\index{while-do}\index{repeat-until}\index{if-then-else}
+The control structures 
+\index{while-do}\index{repeat-until}\index{if-then-else}%
+\T{if}, \T{while}, and \T{repeat} have the usual meaning and
+familiar syntax:
 \begin{Produc}
-\produc{stat}{\rwd{while} exp1 \rwd{do} block \rwd{end} \OrNL
-\rwd{repeat} block \rwd{until} exp1 \OrNL
-\rwd{if} exp1 \rwd{then} block
+\produc{stat}{\rwd{while} exp1 \rwd{do} block \rwd{end}}
+\produc{stat}{\rwd{repeat} block \rwd{until} exp1}
+\produc{stat}{\rwd{if} exp1 \rwd{then} block
   \rep{\rwd{elseif} exp1 \rwd{then} block}
    \opt{\rwd{else} block} \rwd{end}}
-\end{Produc}
+\end{Produc}%
+The \Index{condition expression} \M{exp1} of a control structure may return any value.
+All values different from \nil\ are considered true;
+only \nil\ is considered false.
 
 \index{return}
-A \rwd{return} is used to return values from a function or from a chunk.
+The \rwd{return} statement is used to return values from a function or from a chunk.
 \label{return}
-Because they may return more than one value,
+Because functions or chunks may return more than one value,
 the syntax for a \Index{return statement} is
 \begin{Produc}
 \produc{stat}{\rwd{return} \opt{explist1}}
-\end{Produc}
+\end{Produc}%
 
 \index{break}
-A \rwd{break} statement can be used to terminate the execution of a block,
-skipping to the next instruction after the block.
+The \rwd{break} statement can be used to terminate the execution of a block,
+skipping to the next statement after the block:
 \begin{Produc}
 \produc{stat}{\rwd{break} \opt{name}}
-\end{Produc}
-A \rwd{break} without a label ends the inner enclosing loop
+\end{Produc}%
+A \rwd{break} without a label ends the innermost enclosing loop
 (while, repeat, or for).
-A \rwd{break} with a label breaks the inner enclosing
+A \rwd{break} with a label breaks the innermost enclosing
 statement with that label.
+Thus,
+labels do not have to be unique.
 
 For syntactic reasons, \rwd{return} and \rwd{break}
 statements can only be written as the last statement of a block.
@@ -568,35 +663,36 @@ The \rwd{for} statement has the following syntax:
 \begin{Produc}
 \produc{stat}{\rwd{for} name \ter{=} exp1 \ter{,} exp1 \opt{\ter{,} exp1}
                     \rwd{do} block \rwd{end}}
-\end{Produc}
+\end{Produc}%
 A \rwd{for} statement like
 \begin{verbatim}
-for var=e1,e2,e3 do block end
+   for var=e1,e2,e3 do block end
 \end{verbatim}
 is equivalent to the following code:
 \begin{verbatim}
-do
-  local var, _limit, _step = tonumber(e1), tonumber(e2), tonumber(e3)
-  if not (var and _limit and _step) then error() end
-  while (_step>0 and var<=_limit) or (_step<=0 and var>=_limit) do
-    block
-    var = var+_step
-  end
-end
+   do
+     local var, _limit, _step = tonumber(e1), tonumber(e2), tonumber(e3)
+     if not (var and _limit and _step) then error() end
+     while (_step>0 and var<=_limit) or (_step<=0 and var>=_limit) do
+       block
+       var = var+_step
+     end
+   end
 \end{verbatim}
 Notice the following:
-\begin{itemize}
+\begin{itemize}\itemsep=0pt
 \item \verb|_limit| and \verb|_step| are invisible variables.
-\item The behavior is undefined if you assign to \verb|var| inside
+The names are here for explanatory purposes only.
+\item The behavior is \emph{undefined} if you assign to \verb|var| inside
 the block.
-\item If the third expression (the step) is absent, it defaults to 1.
+\item If the third expression (the step) is absent, then a step of 1 is used.
 \item Both the limit and the step are evaluated only once,
 before the loop starts.
 \item The variable \verb|var| is local to the statement;
-you cannot use its value after the \rwd{for}.
+you cannot use its value after the \rwd{for} ends.
 \item You can use \rwd{break} to exit a \rwd{for}.
 If you need the value of the index,
-assign it to another variable before breaking.
+then assign it to another variable before breaking.
 \end{itemize}
 
 \subsubsection{Function Calls as Statements} \label{funcstat}
@@ -610,8 +706,6 @@ Function calls are explained in \See{functioncall}.
 
 \subsubsection{Local Declarations} \label{localvar}
 \Index{Local variables} may be declared anywhere inside a block.
-Their scope begins after the declaration and lasts until the
-end of the block.
 The declaration may include an initial assignment:
 \begin{Produc}
 \produc{stat}{\rwd{local} declist \opt{init}}
@@ -622,6 +716,13 @@ If present, an initial assignment has the same semantics
 of a multiple assignment.
 Otherwise, all variables are initialized with \nil.
 
+The scope of local variables begins \emph{after}
+the declaration and lasts until the end of the block.
+Thus, the code
+\verb|local print=print|
+creates a local variable called \verb|print| whose
+initial value is that of the \emph{global} variable of the same name.
+
 
 \subsection{\Index{Expressions}}
 
@@ -630,8 +731,8 @@ The basic expressions in Lua are
 \begin{Produc}
 \produc{exp}{\ter{(} exp \ter{)}}
 \produc{exp}{\rwd{nil}}
-\produc{exp}{\ter{number}}
-\produc{exp}{\ter{literal}}
+\produc{exp}{number}
+\produc{exp}{literal}
 \produc{exp}{function}
 \produc{exp}{simpleexp}
 \end{Produc}%
@@ -639,19 +740,21 @@ The basic expressions in Lua are
 \produc{simpleexp}{var}
 \produc{simpleexp}{upvalue}
 \produc{simpleexp}{functioncall}
+\produc{simpleexp}{tableconstructor}
 \end{Produc}%
 
 Numbers (numerical constants) and
-string literals are explained in \See{lexical};
+literal strings are explained in \See{lexical};
 variables are explained in \See{assignment};
 upvalues are explained in \See{upvalue};
 function definitions (\M{function}) are explained in \See{func-def};
 function calls are explained in \See{functioncall}.
+Table constructors are explained in \See{tableconstructor}.
 
 An access to a global variable \verb|x| is equivalent to a
-call \verb|getglobal('x')|;
+call \verb|getglobal("x")|;
 an access to an indexed variable \verb|t[i]| is equivalent to
-a call \verb|gettable_event(t, i)|.
+a call \verb|gettable_event(t,i)|.
 See \See{tag-method} for a description of these functions.
 (Function \verb|getglobal| is pre-defined in Lua.
 Function \T{gettable\_event} is used only for explanatory purposes.)
@@ -660,7 +763,7 @@ The non-terminal \M{exp1} is used to indicate that the values
 returned by an expression must be adjusted to one single value:
 \begin{Produc}
 \produc{exp1}{exp}
-\end{Produc}
+\end{Produc}%
 
 \subsubsection{Arithmetic Operators}
 Lua supports the usual \Index{arithmetic operators}:
@@ -680,7 +783,7 @@ giving the expected meaning to \Index{exponentiation}
 \subsubsection{Relational Operators}
 Lua provides the following \Index{relational operators}:
 \begin{verbatim}
-       ==  ~=  <   >   <=  >=
+   ==  ~=  <   >   <=  >=
 \end{verbatim}
 All these return \nil\ as false and a value different from \nil\ as true.
 
@@ -689,12 +792,13 @@ If they are different, then the result is \nil.
 Otherwise, their values are compared.
 Numbers and strings are compared in the usual way.
 Tables, userdata, and functions are compared by reference,
-that is, two tables are considered equal only if they are the same table.
+that is, two tables are considered equal only if they are the \emph{same} table.
 The operator \verb|~=| is exactly the negation of equality (\verb|==|).
 
+\NOTE
 The conversion rules of \See{coercion}
 \emph{do not} apply to equality comparisons.
-Thus, \verb|"0"==0| evaluates to false,
+Thus, \verb|"0"==0| evaluates to \emph{false},
 and \verb|t[0]| and \verb|t["0"]| denote different
 entries in a table.
 
@@ -702,19 +806,19 @@ The order operators work as follows.
 If both arguments are numbers, then they are compared as such.
 Otherwise, if both arguments are strings,
 then their values are compared using lexicographical order.
-Otherwise, the \verb|"lt"| tag method is called \see{tag-method}.
+Otherwise, the ``lt'' tag method is called \see{tag-method}.
 
 \subsubsection{Logical Operators}
 The \Index{logical operators} are
 \index{and}\index{or}\index{not}
 \begin{verbatim}
-             and   or   not
+   and   or   not
 \end{verbatim}
 Like control structures, all logical operators
 consider \nil\ as false and anything else as true.
-The operator \verb|and| returns \nil\ if its first argument is \nil;
+The conjunction operator \verb|and| returns \nil\ if its first argument is \nil;
 otherwise, it returns its second argument.
-The operator \verb|or| returns its first argument
+The disjunction operator \verb|or| returns its first argument
 if it is different from \nil;
 otherwise, it returns its second argument.
 Both \verb|and| and \verb|or| use \Index{short-cut evaluation},
@@ -722,17 +826,18 @@ that is,
 the second operand is evaluated only when necessary.
 
 There are two useful Lua idioms with logical operators.
-The first is \verb|x = x or v|,
+The first idiom is \verb|x = x or v|,
 which is equivalent to
 \begin{verbatim}
       if x == nil then x = v end
 \end{verbatim}
 i.e., it sets \verb|x| to a default value \verb|v| when
 \verb|x| is not set.
-The other is \verb|x = a and b or c|,
-which is equivalent to
+The other idiom is \verb|x = a and b or c|,
+which should be read as \verb|x = a and (b or c)|,
+is equivalent to
 \begin{verbatim}
-      if a then x = b else x = c end
+   if a then x = b else x = c end
 \end{verbatim}
 provided that \verb|b| is not \nil.
 
@@ -747,21 +852,23 @@ Otherwise, the ``concat'' tag method is called \see{tag-method}.
 \Index{Operator precedence} follows the table below,
 from the lower to the higher priority:
 \begin{verbatim}
-             and   or
-             <   >   <=  >=  ~=  ==
-             ..
-             +   -
-             *   /
-             not  - (unary)
-             ^
+   and   or
+   <   >   <=  >=  ~=  ==
+   ..
+   +   -
+   *   /
+   not  - (unary)
+   ^
 \end{verbatim}
 All binary operators are left associative,
 except for \verb|^| (exponentiation),
 which is right associative.
+\NOTE
 The pre-compiler may rearrange the order of evaluation of
-associative operators (such as \verb|..| or \verb|+|),
+associative operators (such as~\verb|..| or~\verb|+|),
 as long as these optimizations do not change normal results.
-However, they may change some results if you define non-associative
+However, these optimizations may change some results
+if you define non-associative
 tag methods for these operators.
 
 \subsubsection{Table Constructors} \label{tableconstructor}
@@ -769,15 +876,14 @@ Table \Index{constructors} are expressions that create tables;
 every time a constructor is evaluated, a new table is created.
 Constructors can be used to create empty tables,
 or to create a table and initialize some fields.
-
 The general syntax for constructors is
 \begin{Produc}
 \produc{tableconstructor}{\ter{\{} fieldlist \ter{\}}}
 \produc{fieldlist}{lfieldlist \Or ffieldlist \Or lfieldlist \ter{;} ffieldlist
-\Or ffieldlist \ter{;} lfieldlist}
+	\Or ffieldlist \ter{;} lfieldlist}
 \produc{lfieldlist}{\opt{lfieldlist1}}
 \produc{ffieldlist}{\opt{ffieldlist1}}
-\end{Produc}
+\end{Produc}%
 
 The form \emph{lfieldlist1} is used to initialize lists:
 \begin{Produc}
@@ -826,11 +932,11 @@ in fact syntactic sugar for \verb|{["x"] = 1, ["y"] = 4}|.
 Both forms may have an optional trailing comma,
 and can be used in the same constructor separated by
 a semi-collon.
-For example, all forms below are correct:
+For example, all forms below are correct.
 \begin{verbatim}
    x = {;}
-   x = {'a', 'b',}
-   x = {type='list'; 'a', 'b'}
+   x = {"a", "b",}
+   x = {type="list"; "a", "b"}
    x = {f(0), f(1), f(2),; n=3,}
 \end{verbatim}
 
@@ -890,16 +996,17 @@ If the function is called in a place that can hold many values
 then no adjustment is made.
 The only places that can hold many values
 is the last (or the only) expression in an assignment,
-in an argument list, or in a return statement;
-see examples below.
+in an argument list, or in a return statement.
+Here are some examples.
 \begin{verbatim}
-      f();               -- adjusted to 0
-      g(f(), x);         -- f() is adjusted to 1 result
-      g(x, f());         -- g gets x plus all values returned by f()
-      a,b,c = f(), x;    -- f() is adjusted to 1 result (and c gets nil)
-      a,b,c = x, f();    -- f() is adjusted to 2
-      a,b,c = f();       -- f() is adjusted to 3
-      return f();        -- returns all values returned by f()
+   f();               -- adjusted to 0
+   g(f(), x);         -- f() is adjusted to 1 result
+   g(x, f());         -- g gets x plus all values returned by f()
+   a,b,c = f(), x;    -- f() is adjusted to 1 result (and c gets nil)
+   a,b,c = x, f();    -- f() is adjusted to 2
+   a,b,c = f();       -- f() is adjusted to 3
+   return f();        -- returns all values returned by f()
+   return x,y,f();    -- returns a, b, and all values returned by f()
 \end{verbatim}
 
 \subsubsection{\Index{Function Definitions}} \label{func-def}
@@ -910,29 +1017,29 @@ The syntax for function definition is
   block \rwd{end}}
 \produc{stat}{\rwd{function} funcname \ter{(} \opt{parlist1} \ter{)}
   block \rwd{end}}
-\produc{funcname}{name \Or name \ter{.} name}
-\end{Produc}
+\produc{funcname}{name \Or name \ter{.} name \Or name \ter{:} name}
+\end{Produc}%
 The statement
 \begin{verbatim}
-      function f (...)
+      function f ()
         ...
       end
 \end{verbatim}
 is just syntactic sugar for
 \begin{verbatim}
-      f = function (...)
+      f = function ()
             ...
           end
 \end{verbatim}
-and
+and the statement
 \begin{verbatim}
-      function o.f (...)
+      function o.f ()
         ...
       end
 \end{verbatim}
 is syntactic sugar for
 \begin{verbatim}
-      o.f = function (...)
+      o.f = function ()
               ...
             end
 \end{verbatim}
@@ -954,53 +1061,55 @@ initialized with the argument values:
 \begin{Produc}
 \produc{parlist1}{\ter{\ldots}}
 \produc{parlist1}{name \rep{\ter{,} name} \opt{\ter{,} \ter{\ldots}}}
-\end{Produc}
+\end{Produc}%
 \label{vararg}
 When a function is called,
 the list of \Index{arguments} is adjusted to
 the length of the list of parameters \see{adjust},
 unless the function is a \Def{vararg} function,
+which is
 indicated by the dots (\ldots) at the end of its parameter list.
 A vararg function does not adjust its argument list;
-instead, it collects any extra arguments into an implicit parameter,
+instead, it collects all extra arguments into an implicit parameter,
 called \IndexVerb{arg}.
-This parameter is always initialized as a table,
-with a field \verb|n| whose value is the number of extra arguments,
-and the extra arguments at positions 1,~2,~\ldots.
+The value of \verb|arg| is a table,
+with a field~\verb|n| whose value is the number of extra arguments,
+and the extra arguments at positions 1,~2,~\ldots,\M{n}.
 
-As an example, suppose definitions like:
+As an example, consider the following definitions:
 \begin{verbatim}
-      function f(a, b) end
-      function g(a, b, ...) end
-      function r() return 1,2,3 end
+   function f(a, b) end
+   function g(a, b, ...) end
+   function r() return 1,2,3 end
 \end{verbatim}
 Then, we have the following mapping from arguments to parameters:
 \begin{verbatim}
-      CALL            PARAMETERS
+   CALL            PARAMETERS
 
-     f(3)             a=3, b=nil
-     f(3, 4)          a=3, b=4
-     f(3, 4, 5)       a=3, b=4
-     f(r(), 10)       a=1, b=10
-     f(r())           a=1, b=2
+   f(3)             a=3, b=nil
+   f(3, 4)          a=3, b=4
+   f(3, 4, 5)       a=3, b=4
+   f(r(), 10)       a=1, b=10
+   f(r())           a=1, b=2
 
-     g(3)             a=3, b=nil, arg={n=0}
-     g(3, 4)          a=3, b=4, arg={n=0}
-     g(3, 4, 5, 8)    a=3, b=4, arg={5, 8; n=2}
-     g(5, r())        a=5, b=1, arg={2, 3; n=2}
+   g(3)             a=3, b=nil, arg={n=0}
+   g(3, 4)          a=3, b=4, arg={n=0}
+   g(3, 4, 5, 8)    a=3, b=4, arg={5, 8; n=2}
+   g(5, r())        a=5, b=1, arg={2, 3; n=2}
 \end{verbatim}
 
 Results are returned using the \verb|return| statement \see{return}.
-If control reaches the end of a function without a return instruction,
+If control reaches the end of a function
+without encountering a \rwd{return} statement,
 then the function returns with no results.
 
-There is a special syntax for defining \Index{methods},
-that is, functions that have an implicit extra parameter \IndexVerb{self}:
+The syntax
 \begin{Produc}
-\produc{function}{\rwd{function} name \ter{:} name \ter{(} \opt{parlist1}
-  \ter{)} block \rwd{end}}
+\produc{funcname}{name \ter{:} name}
 \end{Produc}%
-Thus, a declaration like
+is used for defining \Index{methods},
+that is, functions that have an implicit extra parameter \IndexVerb{self}:
+Thus, the statement
 \begin{verbatim}
       function v:f (...)
         ...
@@ -1022,28 +1131,31 @@ previously initialized with a table value.
 
 A function body may refer to its own local variables
 (which include its parameters) and to global variables,
-as long as they are not shadowed by local
+as long as they are not \emph{shadowed} by local
 variables from enclosing functions.
 A function \emph{cannot} access a local
 variable from an enclosing function,
 since such variables may no longer exist when the function is called.
 However, a function may access the \emph{value} of a local variable
-from an enclosing function, using \emph{upvalues}.
-
+from an enclosing function, using \emph{upvalues},
+whose syntax is
 \begin{Produc}
 \produc{upvalue}{\ter{\%} name}
-\end{Produc}
+\end{Produc}%
 An upvalue is somewhat similar to a variable expression,
-but whose value is frozen when the function wherein it
+but whose value is \emph{frozen} when the function wherein it
 appears is instantiated.
 The name used in an upvalue may be the name of any variable visible
-at the point where the function is defined.
+at the point where the function is defined,
+that is
+global variables and local variables from the immediately enclosing function.
 
 Here are some examples:
 \begin{verbatim}
       a,b,c = 1,2,3   -- global variables
+      local d
       function f (x)
-        local b       -- x and b are local to f
+        local b       -- x and b are local to f; b shadows the global b
         local g = function (a)
           local y     -- a and y are local to g
           p = a       -- OK, access local 'a'
@@ -1052,11 +1164,50 @@ Here are some examples:
           p = %b      -- OK, access frozen value of 'b' (local to 'f')
           p = %c      -- OK, access frozen value of global 'c'
           p = %y      -- ERROR: 'y' is not visible where 'g' is defined
+          p = %d      -- ERROR: 'd' is not visible where 'g' is defined
         end           -- g
       end             -- f
 \end{verbatim}
 
 
+\subsection{Error Handling} \label{error}
+
+Because Lua is an extension language,
+all Lua actions start from C~code in the host program
+calling a function from the Lua library.
+Whenever an error occurs during Lua compilation or execution,
+the function \verb|_ERRORMESSAGE| is called \Deffunc{_ERRORMESSAGE}
+(provided it is different from \nil),
+and then the corresponding function from the library
+(\verb|lua_dofile|, \verb|lua_dostring|,
+\verb|lua_dobuffer|, or \verb|lua_callfunction|)
+is terminated, returning an error condition.
+
+The only argument to \verb|_ERRORMESSAGE| is a string
+describing the error.
+The default definition for
+this function calls \verb|_ALERT|, \Deffunc{_ALERT}
+which prints the message to \verb|stderr| \see{alert}.
+The standard I/O library redefines \verb|_ERRORMESSAGE|,
+and uses the debug facilities \see{debugI}
+to print some extra information,
+such as a call stack traceback.
+
+To provide more information about errors,
+Lua programs should include the compilation pragma \verb|$debug|,
+\index{debug pragma}\label{pragma}
+or be loaded from the host after calling \verb|lua_setdebug(1)|
+\see{debugI}.
+When an error occurs in a chunk compiled with this option,
+the I/O error-message routine is able to print the number of the
+lines where the calls (and the error) were made.
+
+Lua code can explicitly generate an error by calling the built-in
+function \verb|error| \see{pdf-error}.
+Lua code can ``catch'' an error using the built-in function
+\verb|call| \see{pdf-call}.
+
+
 \subsection{Tag Methods} \label{tag-method}
 
 Lua provides a powerful mechanism to extend its semantics,
@@ -1075,7 +1226,7 @@ Its first parameter is the tag, the second parameter is the event name
 (a string; see below),
 and the third parameter is the new method (a function),
 or \nil\ to restore the default behavior for the pair.
-The function returns the previous tag method for that pair.
+The \verb|settagmethod| function returns the previous tag method for that pair.
 Another function, \IndexVerb{gettagmethod},
 receives a tag and an event name and returns the
 current method associated with the pair.
@@ -1084,9 +1235,9 @@ Tag methods are called in the following events,
 identified by the given names.
 The semantics of tag methods is better explained by a Lua function
 describing the behavior of the interpreter at each event.
-The function not only shows when a tag method is called,
+This function not only shows when a tag method is called,
 but also its arguments, its results, and the default behavior.
-Please notice that the code shown here is only illustrative;
+The code shown here is only \emph{illustrative};
 the real behavior is hard coded in the interpreter,
 and it is much more efficient than this simulation.
 All functions used in these descriptions
@@ -1111,6 +1262,8 @@ If it also fails, then it gets a tag method from tag~0:
                gettagmethod(0, event)
       end
 \end{verbatim}
+Using this function,
+the tag method for the ``add' event is
 \begin{verbatim}
       function add_event (op1, op2)
         local o1, o2 = tonumber(op1), tonumber(op2)
@@ -1131,18 +1284,18 @@ If it also fails, then it gets a tag method from tag~0:
 
 \item[``sub'':]\index{sub event}
 called when a \verb|-| operation is applied to non numerical operands.
-Behavior similar to the \verb|"add"| event.
+Behavior similar to the ``add'' event.
 
 \item[``mul'':]\index{mul event}
 called when a \verb|*| operation is applied to non numerical operands.
-Behavior similar to the \verb|"add"| event.
+Behavior similar to the ``add'' event.
 
 \item[``div'':]\index{div event}
 called when a \verb|/| operation is applied to non numerical operands.
-Behavior similar to the \verb|"add"| event.
+Behavior similar to the ``add'' event.
 
 \item[``pow'':]\index{pow event}
-called when a \verb|^| operation is applied.
+called when a \verb|^| operation (exponentiation) is applied.
 \begin{verbatim}
       function pow_event (op1, op2)
         local tm = getbinmethod(op1, op2, "pow")
@@ -1157,7 +1310,7 @@ called when a \verb|^| operation is applied.
 \end{verbatim}
 
 \item[``unm'':]\index{unm event}
-called when an unary \verb|-| operation is applied to a non numerical operand.
+called when a unary \verb|-| operation is applied to a non numerical operand.
 \begin{verbatim}
       function unm_event (op)
         local o = tonumber(op)
@@ -1228,12 +1381,14 @@ called when a concatenation is applied to non string operands.
 \item[``index'':]\index{index event}
 called when Lua tries to retrieve the value of an index
 not present in a table.
-See event \verb|"gettable"| for its semantics.
+See event ``gettable'' for its semantics.
 
 \item[``getglobal'':]\index{getglobal event}
 called whenever Lua needs the value of a global variable.
 This method can only be set for \nil\ and for tags
 created by \verb|newtag|.
+Note that
+the tag is that of the \emph{current value} of the global variable.
 \begin{verbatim}
       function getglobal (varname)
         local value = rawgetglobal(varname)
@@ -1262,7 +1417,7 @@ userdata with default tags.
         end
       end
 \end{verbatim}
-Notice: the function \verb|setglobal| is pre-defined in Lua \see{predefined}.
+The function \verb|setglobal| is pre-defined in Lua \see{predefined}.
 
 \item[``gettable'':]\index{gettable event}
 called whenever Lua accesses an indexed variable.
@@ -1325,9 +1480,9 @@ called when Lua tries to call a non function value.
 \end{verbatim}
 
 \item[``gc'':]\index{gc event}
-called when Lua is ``garbage collecting'' an userdata.
-This tag method can be set only from C,
-and cannot be set for an userdata with default tag.
+called when Lua is ``garbage collecting'' a userdata.
+This tag method can be set only from~C,
+and cannot be set for a userdata with default tag.
 For each userdata to be collected,
 Lua does the equivalent of the following function:
 \begin{verbatim}
@@ -1345,73 +1500,39 @@ Lua does the equivalent of the call \verb|gc_event(nil)|.
 
 
 
-\subsection{Error Handling} \label{error}
-
-Because Lua is an extension language,
-all Lua actions start from C code in the host program
-calling a function from the Lua library.
-Whenever an error occurs during Lua compilation or execution,
-function \verb|_ERRORMESSAGE| is called \Deffunc{_ERRORMESSAGE}
-(provided it is different from \nil),
-and then the corresponding function from the library
-(\verb|lua_dofile|, \verb|lua_dostring|,
-\verb|lua_dobuffer|, or \verb|lua_callfunction|)
-is terminated, returning an error condition.
-
-The only argument to \verb|_ERRORMESSAGE| is a string
-describing the error.
-The default definition for
-this function calls \verb|_ALERT|, \Deffunc{_ALERT}
-which prints the message to \verb|stderr| \see{alert}.
-The standard I/O library redefines \verb|_ERRORMESSAGE|,
-and uses the debug facilities \see{debugI}
-to print some extra information,
-such as the call stack.
-
-To provide more information about errors,
-Lua programs should include the compilation pragma \verb|$debug|.
-\index{debug pragma}\label{pragma}
-When an error occurs in a chunk compiled with this option,
-the I/O error-message routine is able to print the number of the
-lines where the calls (and the error) were made.
-
-Lua code can explicitly generate an error by calling the built-in
-function \verb|error| \see{pdf-error}.
-Lua code can ``catch'' an error using the built-in function
-\verb|call| \see{pdf-call}.
-
-
 
 \section{The Application Program Interface}
 
 This section describes the API for Lua, that is,
-the set of C functions available to the host program to communicate
+the set of C~functions available to the host program to communicate
 with the Lua library.
-The API functions can be classified in the following categories:
+The API functions can be classified into the following categories:
 \begin{enumerate}
 \item managing states;
 \item exchanging values between C and Lua;
 \item executing Lua code;
 \item manipulating (reading and writing) Lua objects;
 \item calling Lua functions;
-\item defining C functions to be called by Lua;
+\item defining C~functions to be called by Lua;
 \item manipulating references to Lua Objects.
 \end{enumerate}
 All API functions and related types and constants
 are declared in the header file \verb|lua.h|.
 
+\NOTE
 Even when we use the term \emph{function},
 \emph{any facility in the API may be provided as a macro instead}.
-Any of such macros uses once and only once each of its arguments.
+All such macros use each of its arguments exactly once,
+and so do not generate hidden side-effects.
 
 
 \subsection{States} \label{mangstate}
 
-The Lua library is reentrant.
-It does not have any global variable.
+The Lua library is reentrant:
+it does not have any global variable.
 The whole state of the Lua interpreter
-(global variables, stack, tag methods, etc)
-is stored in a dynamic structure \Deffunc{lua_State};
+(global variables, stack, tag methods, etc.)
+is stored in a dynamic structure; \Deffunc{lua_State}
 this state must be passed as the first argument to almost
 every function in the library.
 
@@ -1421,19 +1542,19 @@ This is done by calling\Deffunc{lua_newstate}
 \begin{verbatim}
 lua_State *lua_newstate (const char *s, ...);
 \end{verbatim}
-The arguments to this function is a list of name-value options,
+The arguments to this function form a list of name-value options,
 terminated with \verb|NULL|.
 Currently, the function accepts the following options:
 \begin{itemize}
-\item \verb|"stack"| - the stack size.
+\item \verb|"stack"| --- the stack size.
 Each function call needs one stack position for each local variable
-and temporary variables, plus one position.
+and temporary variables, plus one position for book-keeping.
 The stack must also have at least ten extra positions available.
 For very small implementations, without recursive functions,
-a size of 100 should be enough.
-The default is 1K.
+a stack size of 100 should be enough.
+The default stack size is 1024.
 
-\item \verb|"builtin"| - the value is a boolean (0 or 1) that
+\item \verb|"builtin"| --- the value is a boolean (0 or 1) that
 indicates whether the predefined functions should be loaded or not.
 The default is to load those functions.
 \end{itemize}
@@ -1441,7 +1562,7 @@ For instance, the call
 \begin{verbatim}
 lua_State *L = lua_newstate(NULL);
 \end{verbatim}
-creates a new state with a stack of 1K positions,
+creates a new state with a stack of 1024 positions
 and with the predefined functions loaded;
 the call
 \begin{verbatim}
@@ -1455,13 +1576,18 @@ To release a state, you call
 void lua_close (lua_State *L);
 \end{verbatim}
 This function destroys all objects in the current Lua environment
-(calling the correspondent garbage collector tag methods),
+(calling the corresponding garbage collection tag methods)
 and frees all dynamic memory used by the state.
 Usually, you do not need to call this function,
-because these resources are naturally released when the program ends.
+because all resources are naturally released when the program ends.
+On the other hand,
+long-running programs ---
+like a daemon or web server, for example ---
+might need to release states as soon as they are not needed,
+to avoid growing too big.
 
 With the exception of \verb|lua_newstate|,
-all functions in the API get at its first argument a state.
+all functions in the API need a state as their first argument.
 However, most applications use a single state.
 To avoid the burden of passing this only state explicitly to all
 functions, and also to keep compatibility with old versions of Lua,
@@ -1491,14 +1617,13 @@ in this case, the corresponding macro is
 \begin{verbatim}
 #define lua_open()      ((void)(lua_state?0:(lua_state=lua_newstate(0))))
 \end{verbatim}
-It checks whether the global state has been initialized;
+This code checks whether the global state has been initialized;
 if not, it creates a new state with default settings and
 assigns it to \verb|lua_newstate|.
 
-By default, those macros are all active.
-If you will use multiple states,
-and therefore will want to provide the state
-argument explicitly for each call,
+By default, the single-state macros are all active.
+If you need to use multiple states,
+and therefore will provide the state argument explicitly in each call,
 you should define \IndexVerb{LUA_REENTRANT} before
 including \verb|lua.h| in your code:
 \begin{verbatim}
@@ -1520,7 +1645,7 @@ which works like an abstract type in C that can hold any Lua value.
 Values of type \verb|lua_Object| have no meaning outside Lua;
 for instance,
 you cannot compare two \verb|lua_Object's| directly.
-Instead, you should use the next function:
+Instead, you should use the following function:
 \Deffunc{lua_equal}
 \begin{verbatim}
 int lua_equal       (lua_Object o1, lua_Object o2);
@@ -1533,21 +1658,21 @@ the following functions are available:
 \Deffunc{lua_isfunction}
 \Deffunc{lua_type}
 \begin{verbatim}
-int lua_isnil       (lua_Object object);
-int lua_isnumber    (lua_Object object);
-int lua_isstring    (lua_Object object);
-int lua_istable     (lua_Object object);
-int lua_isfunction  (lua_Object object);
-int lua_iscfunction (lua_Object object);
-int lua_isuserdata  (lua_Object object);
-const char *lua_type (lua_Object obj);
+int lua_isnil        (lua_Object object);
+int lua_isnumber     (lua_Object object);
+int lua_isstring     (lua_Object object);
+int lua_istable      (lua_Object object);
+int lua_isfunction   (lua_Object object);
+int lua_iscfunction  (lua_Object object);
+int lua_isuserdata   (lua_Object object);
+const char *lua_type (lua_Object object);
 \end{verbatim}
 The \verb|lua_is*| functions return 1 if the object is compatible
 with the given type, and 0 otherwise.
 The function \verb|lua_isnumber| accepts numbers and numerical strings,
 \verb|lua_isstring| accepts strings and numbers \see{coercion},
-and \verb|lua_isfunction| accepts Lua functions and C functions.
-To distinguish between Lua functions and C functions,
+and \verb|lua_isfunction| accepts Lua functions and C~functions.
+To distinguish between Lua functions and C~functions,
 you should use \verb|lua_iscfunction|.
 To distinguish between numbers and numerical strings,
 you can use \verb|lua_type|.
@@ -1557,14 +1682,14 @@ describing the type of the given object:
 \verb|"function"|, \verb|"userdata"|, or \verb|"NOOBJECT"|.
 
 To get the tag of a \verb|lua_Object|,
-the following function is available:
+use the following function:
 \Deffunc{lua_tag}
 \begin{verbatim}
 int lua_tag (lua_Object object);
 \end{verbatim}
 
 To translate a value from type \verb|lua_Object| to a specific C type,
-you can use
+you can use the following conversion functions:
 \Deffunc{lua_getnumber}\Deffunc{lua_getstring}\Deffunc{lua_strlen}
 \Deffunc{lua_getcfunction}\Deffunc{lua_getuserdata}
 \begin{verbatim}
@@ -1593,9 +1718,13 @@ Because Lua has garbage collection,
 there is no guarantee that the pointer returned by \verb|lua_getstring|
 will be valid after the block ends
 \see{GC}.
+So,
+if you need the string later on,
+you should duplicate it with something like
+\verb|memcpy(malloc(lua_strlen(o),lua_getstring(o)))|.
 
-\verb|lua_getcfunction| converts a \verb|lua_Object| to a C function.
-This \verb|lua_Object| must have type \emph{CFunction};
+\verb|lua_getcfunction| converts a \verb|lua_Object| to a C~function.
+This \verb|lua_Object| must be a C~function;
 otherwise, \verb|lua_getcfunction| returns \verb|NULL|.
 The type \verb|lua_CFunction| is explained in \See{LuacallC}.
 
@@ -1603,27 +1732,7 @@ The type \verb|lua_CFunction| is explained in \See{LuacallC}.
 This \verb|lua_Object| must have type \emph{userdata};
 otherwise, \verb|lua_getuserdata| returns \verb|NULL|.
 
-\subsection{Garbage Collection}\label{GC}
-Because Lua has automatic memory management and garbage collection,
-a \verb|lua_Object| has a limited scope,
-and is only valid inside the \emph{block} where it has been created.
-A C function called from Lua is a block,
-and its parameters are valid only until its end.
-It is good programming practice to convert Lua objects to C values
-as soon as they are available,
-and never to store \verb|lua_Object|s in C global variables.
-
-A garbage collection cycle can be forced by:
-\Deffunc{lua_collectgarbage}
-\begin{verbatim}
-long lua_collectgarbage (long limit);
-\end{verbatim}
-This function returns the number of objects collected.
-The argument \verb|limit| makes the next cycle occur only
-after that number of new objects have been created.
-If \verb|limit| is 0,
-then Lua uses an adaptive heuristics to set this limit.
-
+\subsection{Communication between Lua and C}\label{Lua-C-protocol}
 
 All communication between Lua and C is done through two
 abstract data types, called \Def{lua2C} and \Def{C2lua}.
@@ -1633,8 +1742,8 @@ parameters when Lua calls C and results when C calls Lua.
 The structure C2lua is used in the reverse direction:
 parameters when C calls Lua and results when Lua calls C.
 
-The structure lua2C is an abstract array,
-which can be indexed with the function:
+The structure lua2C is an \emph{abstract array}
+that can be indexed with the function:
 \Deffunc{lua_lua2C}
 \begin{verbatim}
 lua_Object lua_lua2C (int number);
@@ -1642,12 +1751,12 @@ lua_Object lua_lua2C (int number);
 where \verb|number| starts with 1.
 When called with a number larger than the array size,
 this function returns \verb|LUA_NOOBJECT|\Deffunc{LUA_NOOBJECT}.
-In this way, it is possible to write C functions that receive
+In this way, it is possible to write C~functions that receive
 a variable number of parameters,
 and to call Lua functions that return a variable number of results.
 Note that the structure lua2C cannot be directly modified by C code.
 
-The second structure, C2lua, is an abstract stack.
+The structure C2lua is an \emph{abstract stack}.
 Pushing elements into this stack
 is done with the following functions:
 \Deffunc{lua_pushnumber}\Deffunc{lua_pushlstring}\Deffunc{lua_pushstring}
@@ -1670,7 +1779,7 @@ In particular, functions \verb|lua_pushlstring| and \verb|lua_pushstring|
 make an internal copy of the given string.
 Function \verb|lua_pushstring| can only be used to push proper C strings
 (that is, strings that end with a zero and do not contain embedded zeros);
-otherwise you should use the more generic \verb|lua_pushlstring|.
+otherwise you should use the more general \verb|lua_pushlstring|.
 The function
 \Deffunc{lua_pop}
 \begin{verbatim}
@@ -1682,10 +1791,48 @@ and pops it.
 As a general rule, all API functions pop from the stack
 all elements they use.
 
+When C code calls Lua repeatedly, as in a loop,
+objects returned by these calls can accumulate,
+and may cause a stack overflow.
+To avoid this,
+nested blocks can be defined with the functions
+\begin{verbatim}
+void lua_beginblock (void);
+void lua_endblock   (void);
+\end{verbatim}
+After the end of the block,
+all \verb|lua_Object|'s created inside it are released.
+The use of explicit nested blocks is good programming practice
+and is strongly encouraged.
+
+\subsection{Garbage Collection}\label{GC}
+Because Lua has automatic memory management and garbage collection,
+a \verb|lua_Object| has a limited scope,
+and is only valid inside the \emph{block} where it has been created.
+A C~function called from Lua is a block,
+and its parameters are valid only until its end.
+It is good programming practice to convert Lua objects to C values
+as soon as they are available,
+and never to store \verb|lua_Object|s in C global variables.
+
+A garbage collection cycle can be forced by:
+\Deffunc{lua_collectgarbage}
+\begin{verbatim}
+long lua_collectgarbage (long limit);
+\end{verbatim}
+This function returns the number of objects collected.
+The argument \verb|limit| makes the next cycle occur only
+after that number of new objects have been created.
+If \verb|limit| is 0,
+then Lua uses an adaptive heuristics to set this limit.
+
+
+\subsection{Userdata and Tags}\label{C-tags}
+
 Because userdata are objects,
 the function \verb|lua_pushusertag| may create a new userdata.
 If Lua has a userdata with the given value (\verb|void*|) and tag,
-that userdata is pushed.
+then that userdata is pushed.
 Otherwise, a new userdata is created, with the given value and tag.
 If this function is called with
 \verb|tag| equal to \verb|LUA_ANYTAG|\Deffunc{LUA_ANYTAG},
@@ -1696,38 +1843,24 @@ with tag equal to 0.
 
 Userdata can have different tags,
 whose semantics are only known to the host program.
-Tags are created with the function:
+Tags are created with the function
 \Deffunc{lua_newtag}
 \begin{verbatim}
 int lua_newtag (void);
 \end{verbatim}
 The function \verb|lua_settag| changes the tag of
 the object on the top of C2lua (and pops it);
-the object must be a userdata or a table.
+the object must be a userdata or a table:
 \Deffunc{lua_settag}
 \begin{verbatim}
 void lua_settag (int tag);
 \end{verbatim}
-\verb|tag| must be a value created with \verb|lua_newtag|.
+The given \verb|tag| must be a value created with \verb|lua_newtag|.
 
-When C code calls Lua repeatedly, as in a loop,
-objects returned by these calls can accumulate,
-and may cause a stack overflow.
-To avoid this,
-nested blocks can be defined with the functions:
-\begin{verbatim}
-void lua_beginblock (void);
-void lua_endblock   (void);
-\end{verbatim}
-After the end of the block,
-all \verb|lua_Object|'s created inside it are released.
-The use of explicit nested blocks is good programming practice
-and is strongly encouraged.
-
-\subsection{Executing Lua Code}
-A host program can execute Lua chunks written in a file or in a string
-using the following functions:%
-\Deffunc{lua_dofile}\Deffunc{lua_dostring}\Deffunc{lua_dobuffer}
+\subsection{Executing Lua Code}
+A host program can execute Lua chunks written in a file or in a string
+using the following functions:%
+\Deffunc{lua_dofile}\Deffunc{lua_dostring}\Deffunc{lua_dobuffer}
 \begin{verbatim}
 int lua_dofile   (const char *filename);
 int lua_dostring (const char *string);
@@ -1737,19 +1870,25 @@ All these functions return an error code:
 0, in case of success; non zero, in case of errors.
 More specifically, \verb|lua_dofile| returns 2 if for any reason
 it could not open the file.
+(In this case,
+you may want to
+check \verb|errno|,
+call \verb|strerror|,
+or call \verb|perror| to tell the user what went wrong.)
 When called with argument \verb|NULL|,
 \verb|lua_dofile| executes the \verb|stdin| stream.
 Functions \verb|lua_dofile| and \verb|lua_dobuffer|
 are both able to execute pre-compiled chunks.
 They automatically detect whether the chunk is text or binary,
 and load it accordingly (see program \IndexVerb{luac}).
-Function \verb|lua_dostring| executes only source code.
+Function \verb|lua_dostring| executes only source code,
+given in textual form.
 
 The third parameter to \verb|lua_dobuffer| (\verb|name|)
 is the ``name of the chunk'',
 used in error messages and debug information.
 If \verb|name| is \verb|NULL|,
-Lua gives a default name to the chunk.
+then Lua gives a default name to the chunk.
 
 These functions return, in structure lua2C,
 any values eventually returned by the chunks.
@@ -1758,12 +1897,13 @@ They also empty the stack C2lua.
 
 \subsection{Manipulating Lua Objects}
 To read the value of any global Lua variable,
-one uses the function:
+one uses the function
 \Deffunc{lua_getglobal}
 \begin{verbatim}
 lua_Object lua_getglobal (const char *varname);
 \end{verbatim}
-As in Lua, this function may trigger a tag method.
+As in Lua, this function may trigger a tag method
+for the ``getglobal'' event.
 To read the real value of any global variable,
 without invoking any tag method,
 use the \emph{raw} version:
@@ -1773,12 +1913,13 @@ lua_Object lua_rawgetglobal (const char *varname);
 \end{verbatim}
 
 To store a value previously pushed onto C2lua in a global variable,
-there is the function:
+there is the function
 \Deffunc{lua_setglobal}
 \begin{verbatim}
 void lua_setglobal (const char *varname);
 \end{verbatim}
-As in Lua, this function may trigger a tag method.
+As in Lua, this function may trigger a tag method
+for the ``setglobal'' event.
 To set the real value of any global variable,
 without invoking any tag method,
 use the \emph{raw} version:
@@ -1795,7 +1936,8 @@ lua_Object lua_gettable (void);
 \end{verbatim}
 pops a table and an index from the stack C2lua,
 and returns the contents of the table at that index.
-As in Lua, this operation may trigger a tag method.
+As in Lua, this operation may trigger a tag method
+for the ``gettable'' event.
 To get the real value of any table index,
 without invoking any tag method,
 use the \emph{raw} version:
@@ -1805,14 +1947,15 @@ lua_Object lua_rawgettable (void);
 \end{verbatim}
 
 To store a value in an index,
-the program must push the table, the index,
-and the value onto C2lua,
+the program must push the table, the index, and the value onto C2lua
+(in this order),
 and then call the function
 \Deffunc{lua_settable}
 \begin{verbatim}
 void lua_settable (void);
 \end{verbatim}
-Again, the tag method for ``settable'' may be called.
+As in Lua, this operation may trigger a tag method
+for the ``settable'' event.
 To set the real value of any table index,
 without invoking any tag method,
 use the \emph{raw} version:
@@ -1846,11 +1989,11 @@ Finally, the results are returned in structure lua2C
 (recall that a Lua function may return many values),
 and can be retrieved with the macro \verb|lua_getresult|,
 \Deffunc{lua_getresult}
-which is just another name to function \verb|lua_lua2C|.
-Note that function \verb|lua_callfunction|
+which is just another name for the function \verb|lua_lua2C|.
+Note that \verb|lua_callfunction|
 pops all elements from the C2lua stack.
 
-The following example shows how a C program may do the
+The following example shows how the host program may do the
 equivalent to the Lua code:
 \begin{verbatim}
       a,b = f("how", t.x, 4)
@@ -1869,18 +2012,19 @@ equivalent to the Lua code:
 \end{verbatim}
 
 Some special Lua functions have exclusive interfaces.
-A C function can generate a Lua error calling the function
+The host program can generate a Lua error calling the function
 \Deffunc{lua_error}
 \begin{verbatim}
 void lua_error (const char *message);
 \end{verbatim}
 This function never returns.
-If the C function has been called from Lua,
+If \verb|lua_error| is called from a C~function that has been called from Lua,
 then the corresponding Lua execution terminates,
 as if an error had occurred inside Lua code.
 Otherwise, the whole host program terminates with a call to \verb|exit(1)|.
-The \verb|message| is passed to the error handler function,
-\verb|_ERRORMESSAGE|.
+Before terminating execution,
+the \verb|message| is passed to the error handler function,
+\verb|_ERRORMESSAGE| \see{error}.
 If \verb|message| is \verb|NULL|,
 then \verb|_ERRORMESSAGE| is not called.
 
@@ -1915,7 +2059,7 @@ and the second is a \emph{cursor};
 this cursor starts in 0,
 and for each call the function returns a value to
 be used in the next call,
-or 0 to signal the end of the traverse.
+or 0 to signal the end of the traversal.
 The function also returns, in the Lua2C array,
 a key-value pair from the table.
 A typical traversal looks like the following code:
@@ -1936,9 +2080,9 @@ A typical traversal looks like the following code:
 \end{verbatim}
 The pairs of \verb|lua_beginblock|/\verb|lua_endblock| remove the
 results of each iteration from the stack.
-Without them, a traversal of a large table will overflow the stack.
+Without them, a traversal of a large table may overflow the stack.
 
-To traverse the global variables, you use \Deffunc{lua_nextvar}
+To traverse the global variables, use \Deffunc{lua_nextvar}
 \begin{verbatim}
 const char *lua_nextvar (const char *varname);
 \end{verbatim}
@@ -1964,8 +2108,8 @@ A typical traversal looks like the following code:
 
 
 \subsection{Defining C Functions} \label{LuacallC}
-To register a C function to Lua,
-there is the following macro:
+To register a C~function to Lua,
+there is the following convenience macro:
 \Deffunc{lua_register}
 \begin{verbatim}
 #define lua_register(n,f)       (lua_pushcfunction(f), lua_setglobal(n))
@@ -1983,39 +2127,42 @@ typedef void (*lua_CFunction) (void);
 that is, a pointer to a function with no parameters and no results.
 
 In order to communicate properly with Lua,
-a C function must follow a protocol,
+a C~function must follow a protocol,
 which defines the way parameters and results are passed.
 
-A C function receives its arguments in structure lua2C;
+A C~function receives its arguments in structure lua2C;
 to access them, it uses the macro \verb|lua_getparam|, \Deffunc{lua_getparam}
 again just another name for \verb|lua_lua2C|.
-To return values, a C function just pushes them onto the stack C2lua,
+To return values, a C~function just pushes them onto the stack C2lua,
 in direct order \see{valuesCLua}.
-Like a Lua function, a C function called by Lua can also return
+Like a Lua function, a C~function called by Lua can also return
 many results.
 
-When a C function is created,
-it is possible to associate some \emph{upvalues} to it,
+When a C~function is created,
+it is possible to associate some \emph{upvalues} to it
+\see{upvalue},
 thus creating a C closure;
-then these values are passed to the function whenever it is called,
+these values are passed to the function whenever it is called,
 as common arguments.
-To associate upvalues to a function,
+To associate upvalues to a C~function,
 first these values must be pushed on C2lua.
 Then the function \Deffunc{lua_pushcclosure}
 \begin{verbatim}
 void lua_pushcclosure (lua_CFunction fn, int n);
 \end{verbatim}
-is used to put the C function on C2lua,
+is used to put the C~function on C2lua,
 with the argument \verb|n| telling how many upvalues must be
 associated with the function;
 in fact, the macro \verb|lua_pushcfunction| is defined as
 \verb|lua_pushcclosure| with \verb|n| set to 0.
-Then, any time the function is called,
-these upvalues are inserted as the first arguments to the function,
+Then, whenever the C~function is called,
+these upvalues are inserted as the first arguments \M{n} to the function,
 before the actual arguments provided in the call.
 
-For some examples of C functions, see files \verb|lstrlib.c|,
+For some examples of C~functions, see files \verb|lstrlib.c|,
 \verb|liolib.c| and \verb|lmathlib.c| in the official Lua distribution.
+In particular,
+\verb|liolib.c| defines C~closures with file handles are upvalues.
 
 \subsection{References to Lua Objects}
 
@@ -2034,15 +2181,15 @@ void       lua_unref  (int ref);
 The function \verb|lua_ref| creates a reference
 to the object that is on the top of the stack,
 and returns this reference.
-For a \nil{} object,
+For a \nil\ object,
 the reference is always \verb|LUA_REFNIL|;\Deffunc{LUA_REFNIL}
 otherwise, it is a non-negative integer.
 The constant \verb|LUA_NOREF| \Deffunc{LUA_NOREF}
 is different from any valid reference.
-If \verb|lock| is true, the object is \emph{locked}:
+If \verb|lock| is true, then the object is \emph{locked}:
 this means the object will not be garbage collected.
-Note that an unlocked reference may be garbage collected.
-Whenever the referenced object is needed,
+\emph{Unlocked references may be garbage collected}.
+Whenever the referenced object is needed in~C,
 a call to \verb|lua_getref|
 returns a handle to it;
 if the object has been collected,
@@ -2081,6 +2228,28 @@ and \verb|lua_iolibopen|, declared in \verb|lualib.h|.
 
 \subsection{Predefined Functions} \label{predefined}
 
+\subsubsection*{\ff \T{_ALERT (message)}}\Deffunc{alert}\label{alert}
+Prints its only string argument to \IndexVerb{stderr}.
+All error messages in Lua are printed through the function stored
+in the \verb|_ALERT| global variable
+\see{error}.
+Therefore, a program may assign another function to this variable
+to change the way such messages are shown
+(for instance, for systems without \verb|stderr|).
+
+\subsubsection*{\ff \T{assert (v [, message])}}\Deffunc{assert}
+Issues an \emph{``assertion failed!''} error
+when its argument \verb|v| is \nil.
+This function is equivalent to the following Lua function:
+\begin{verbatim}
+      function assert (v, m)
+        if not v then
+          m = m or ""
+          error("assertion failed!  " .. m)
+        end
+      end
+\end{verbatim}
+
 \subsubsection*{\ff \T{call (func, arg [, mode [, errhandler]])}}\Deffunc{call}
 \label{pdf-call}
 Calls function \verb|func| with
@@ -2092,24 +2261,24 @@ The call is equivalent to
 where \verb|n| is the result of \verb|getn(arg)| \see{getn}.
 
 By default,
-all results from \verb|func| are just returned by the call.
+all results from \verb|func| are simply returned by \verb|call|.
 If the string \verb|mode| contains \verb|"p"|,
-the results are \emph{packed} in a single table.\index{packed results}
+then the results are \emph{packed} in a single table.\index{packed results}
 That is, \verb|call| returns just one table;
 at index \verb|n|, the table has the total number of results
 from the call;
 the first result is at index 1, etc.
 For instance, the following calls produce the following results:
 \begin{verbatim}
-a = call(sin, {5})                --> a = 0.0871557 = sin(5)
-a = call(max, {1,4,5; n=2})       --> a = 4 (only 1 and 4 are arguments)
-a = call(max, {1,4,5; n=2}, "p")  --> a = {4; n=1}
-t = {x=1}
-a = call(next, {t,nil;n=2}, "p")  --> a={"x", 1; n=2}
+   a = call(sin, {5})                --> a = 0.0871557 = sin(5)
+   a = call(max, {1,4,5; n=2})       --> a = 4 (only 1 and 4 are arguments)
+   a = call(max, {1,4,5; n=2}, "p")  --> a = {4; n=1}
+   t = {x=1}
+   a = call(next, {t,nil;n=2}, "p")  --> a={"x", 1; n=2}
 \end{verbatim}
 
 By default,
-if an error occurs during the function call,
+if an error occurs during the call to \verb|func|,
 the error is propagated.
 If the string \verb|mode| contains \verb|"x"|,
 then the call is \emph{protected}.\index{protected calls}
@@ -2118,26 +2287,31 @@ regardless of what happens during the call.
 Instead, it returns \nil\ to signal the error
 (besides calling the appropriated error handler).
 
-If provided,
-\verb|errhandler| is temporarily set as the error function
-\verb|_ERRORMESSAGE|, while \verb|func| runs.
+If \verb|errhandler| is provided,
+the error function \verb|_ERRORMESSAGE| is temporarily set \verb|errhandler|,
+while \verb|func| runs.
 In particular, if \verb|errhandler| is \nil,
 no error messages will be issued during the execution of the called function.
 
 \subsubsection*{\ff \T{collectgarbage ([limit])}}\Deffunc{collectgarbage}
 Forces a garbage collection cycle.
 Returns the number of objects collected.
-An optional argument, \verb|limit|, is a number that
+The optional argument \verb|limit| is a number that
 makes the next cycle occur only after that number of new
 objects have been created.
 If \verb|limit| is absent or equal to 0,
-Lua uses an adaptive algorithm to set this limit.
+then Lua uses an adaptive algorithm to set this limit.
 \verb|collectgarbage| is equivalent to
 the API function \verb|lua_collectgarbage|.
 
+\subsubsection*{\ff \T{copytagmethods (tagto, tagfrom)}}
+\Deffunc{copytagmethods}
+Copies all tag methods from one tag to another;
+it returns \verb|tagto|.
+
 \subsubsection*{\ff \T{dofile (filename)}}\Deffunc{dofile}
 Receives a file name,
-opens the file, and executes the file contents as a Lua chunk,
+opens the named file, and executes its contents as a Lua chunk,
 or as pre-compiled chunks.
 When called without arguments,
 \verb|dofile| executes the contents of the standard input (\verb|stdin|).
@@ -2151,14 +2325,140 @@ It issues an error when called with a non string argument.
 \subsubsection*{\ff \T{dostring (string [, chunkname])}}\Deffunc{dostring}
 Executes a given string as a Lua chunk.
 If there is any error executing the string,
-\verb|dostring| returns \nil.
+then \verb|dostring| returns \nil.
 Otherwise, it returns the values returned by the chunk,
 or a non \nil\ value if the chunk returns no values.
-An optional second parameter (\verb|chunkname|)
+The optional parameter \verb|chunkname|
 is the ``name of the chunk'',
 used in error messages and debug information.
 \verb|dostring| is equivalent to the API function \verb|lua_dostring|.
 
+\subsubsection*{\ff \T{error (message)}}\Deffunc{error}\label{pdf-error}
+Calls the error handler \see{error} and then terminates
+the last protected function called
+(in~C: \verb|lua_dofile|, \verb|lua_dostring|,
+\verb|lua_dobuffer|, or \verb|lua_callfunction|;
+in Lua: \verb|dofile|, \verb|dostring|, or \verb|call| in protected mode).
+If \verb|message| is \nil, then the error handler is not called.
+Function \verb|error| never returns.
+\verb|error| is equivalent to the API function \verb|lua_error|.
+
+\subsubsection*{\ff \T{foreach (table, function)}}\Deffunc{foreach}
+Executes the given \verb|function| over all elements of \verb|table|.
+For each element, the function is called with the index and
+respective value as arguments.
+If the function returns any non-\nil\ value,
+then the loop is broken, and this value is returned
+as the final value of \verb|foreach|.
+
+This function could be defined in Lua:
+\begin{verbatim}
+      function foreach (t, f)
+        local i, v = nil
+        while 1 do
+          i, v = next(t, i)
+          if not i then break end
+          local res = f(i, v)
+          if res then return res end
+        end
+      end
+\end{verbatim}
+
+You may change the \emph{values} of existing fields in the table during the traversal,
+but
+if you create new indices,
+then
+the semantics of \verb|foreach| is undefined.
+
+
+\subsubsection*{\ff \T{foreachi (table, function)}}\Deffunc{foreachi}
+Executes the given \verb|function| over the
+numerical indices of \verb|table|.
+For each index, the function is called with the index and
+respective value as arguments.
+Indices are visited in sequential order,
+from 1 to \verb|n|,
+where \verb|n| is the result of \verb|getn(table)| \see{getn}.
+If the function returns any non-\nil\ value,
+then the loop is broken, and this value is returned
+as the final value of \verb|foreachi|.
+
+This function could be defined in Lua:
+\begin{verbatim}
+      function foreachi (t, f)
+        for i=1,getn(t) do
+          local res = f(i, t[i])
+          if res then return res end
+        end
+      end
+\end{verbatim}
+
+You may change the \emph{values} of existing fields in the table during the traversal,
+but
+if you create new indices (even non-numeric),
+then
+the semantics of \verb|foreachi| is undefined.
+
+\subsubsection*{\ff \T{foreachvar (function)}}\Deffunc{foreachvar}
+Executes \verb|function| over all global variables.
+For each variable,
+the function is called with its name and its value as arguments.
+If the function returns any non-nil value,
+then the loop is broken, and this value is returned
+as the final value of \verb|foreachvar|.
+
+This function could be defined in Lua:
+\begin{verbatim}
+      function foreachvar (f)
+        local n, v = nil
+        while 1 do
+          n, v = nextvar(n)
+          if not n then break end
+          local res = f(n, v)
+          if res then return res end
+        end
+      end
+\end{verbatim}
+
+You may change the values of existing global variables during the traversal,
+but
+if you create new global variables,
+then
+the semantics of \verb|foreachvar| is undefined.
+
+
+\subsubsection*{\ff \T{getglobal (name)}}\Deffunc{getglobal}
+Gets the value of a global variable,
+or calls a tag method for ``getgloball''.
+Its full semantics is explained in \See{tag-method}.
+The string \verb|name| does not need to be a
+syntactically valid variable name.
+
+\subsubsection*{\ff \T{getn (table)}}\Deffunc{getn}\label{getn}
+Returns the ``size'' of a table, when seen as a list.
+If the table has an \verb|n| field with a numeric value,
+this value is its ``size''.
+Otherwise, the size is the largest numerical index with a non-nil
+value in the table.
+This function could be defined in Lua:
+\begin{verbatim}
+      function getn (t)
+        if type(t.n) == 'number' then return t.n end
+        local max, i = 0, nil
+        while 1 do
+          i = next(t, i)
+          if not i then break end
+          if type(i) == 'number' and i>max then max=i end
+        end
+        return max
+      end
+\end{verbatim}
+
+\subsubsection*{\ff \T{gettagmethod (tag, event)}}
+\Deffunc{gettagmethod}
+Returns the current tag method
+for a given pair \M{(tag, event)}.
+
 \subsubsection*{\ff \T{newtag ()}}\Deffunc{newtag}\label{pdf-newtag}
 Returns a new tag.
 \verb|newtag| is equivalent to the API function \verb|lua_newtag|.
@@ -2170,23 +2470,26 @@ is an index in this table.
 It returns the next index of the table and the
 value associated with the index.
 When called with \nil\ as its second argument,
-the function returns the first index
-of the table (and its associated value).
+\verb|next| returns the first index
+of the table and its associated value.
 When called with the last index,
 or with \nil\ in an empty table,
 it returns \nil.
-If the second argument is absent, it is interpreted as \nil.
+If the second argument is absent, then it is interpreted as \nil.
 
 Lua has no declaration of fields;
 semantically, there is no difference between a
 field not present in a table or a field with value \nil.
-Therefore, the function only considers fields with non \nil\ values.
+Therefore, \verb|next| only considers fields with non \nil\ values.
 The order in which the indices are enumerated is not specified,
 \emph{even for numeric indices}
 (to traverse a table in numeric order,
 use a counter or the function \verb|foreachi|).
-If you create new indices in a table while
-traversing it,
+
+You may change the \emph{values} of existing fields in the table during the traversal,
+but
+if you create new indices,
+then
 the semantics of \verb|next| is undefined.
 
 \subsubsection*{\ff \T{nextvar (name)}}\Deffunc{nextvar}
@@ -2194,18 +2497,16 @@ This function is similar to the function \verb|next|,
 but iterates instead over the global variables.
 Its single argument is the name of a global variable,
 or \nil\ to get a first name.
-If this argument is absent, it is interpreted as \nil.
-Similarly to \verb|next|, it returns the name of another variable
+If this argument is absent, then it is interpreted as \nil.
+Like \verb|next|, \verb|nextvar| returns the name of another variable
 and its value,
 or \nil\ if there are no more variables.
-If you create new global variables during the traversal,
-the semantics of \verb|nextvar| is undefined.
 
-\subsubsection*{\ff \T{tostring (e)}}\Deffunc{tostring}
-Receives an argument of any type and
-converts it to a string in a reasonable format.
-For complete control on how numbers are converted,
-use function \verb|format|.
+You may change the \emph{values} of existing global variables during the traversal,
+but
+if you create new global variables,
+then
+the semantics of \verb|nextvar| is undefined.
 
 \subsubsection*{\ff \T{print (e1, e2, ...)}}\Deffunc{print}
 Receives any number of arguments,
@@ -2215,77 +2516,11 @@ but only as a quick way to show a value,
 for instance for debugging.
 See \See{libio} for functions for formatted output.
 
-\subsubsection*{\ff \T{_ALERT (message)}}\Deffunc{alert}\label{alert}
-Prints its only string argument to \IndexVerb{stderr}.
-All error messages in Lua are printed through the function stored
-in the \verb|_ALERT| global variable.
-Therefore, a program may assign another function to this variable
-to change the way such messages are shown
-(for instance, for systems without \verb|stderr|).
-
-\subsubsection*{\ff \T{tonumber (e [, base])}}\Deffunc{tonumber}
-Receives one argument,
-and tries to convert it to a number.
-If the argument is already a number or a string convertible
-to a number, then \verb|tonumber| returns that number;
-otherwise, it returns \nil.
-
-An optional argument specifies the base to interpret the numeral.
-The base may be any integer between 2 and 36 inclusive.
-In bases above  10, the letter `A' (either upper or lower case)
-represents 10, `B' represents 11, and so forth, with `Z' representing 35.
-
-In base 10 (the default), the number may have a decimal part,
-as well as an optional exponent part \see{coercion}.
-In other bases, only unsigned integers are accepted.
-
-\subsubsection*{\ff \T{type (v)}}\Deffunc{type}\label{pdf-type}
-Allows Lua to test the type of a value.
-It receives one argument, and returns its type, coded as a string.
-The possible results of this function are
-\verb|"nil"| (a string, not the value \nil),
-\verb|"number"|,
-\verb|"string"|,
-\verb|"table"|,
-\verb|"function"|,
-and \verb|"userdata"|.
-
-\subsubsection*{\ff \T{tag (v)}}\Deffunc{tag}\label{pdf-tag}
-Allows Lua to test the tag of a value \see{TypesSec}.
-It receives one argument, and returns its tag (a number).
-\verb|tag| is equivalent to the API function \verb|lua_tag|.
-
-\subsubsection*{\ff \T{settag (t, tag)}}\Deffunc{settag}
-Sets the tag of a given table \see{TypesSec}.
-\verb|tag| must be a value created with \verb|newtag|
-\see{pdf-newtag}.
-It returns the value of its first argument (the table).
-For security reasons,
-it is impossible to change the tag of a userdata from Lua.
-
-
-\subsubsection*{\ff \T{assert (v [, message])}}\Deffunc{assert}
-Issues an \emph{``assertion failed!''} error
-when its argument is \nil.
-This function is equivalent to the following Lua function:
-\begin{verbatim}
-      function assert (v, m)
-        if not v then
-          m = m or ""
-          error("assertion failed!  " .. m)
-        end
-      end
-\end{verbatim}
-
-\subsubsection*{\ff \T{error (message)}}\Deffunc{error}\label{pdf-error}
-Calls the error handler and then terminates
-the last protected function called
-(in~C: \verb|lua_dofile|, \verb|lua_dostring|,
-\verb|lua_dobuffer|, or \verb|lua_callfunction|;
-in Lua: \verb|dofile|, \verb|dostring|, or \verb|call| in protected mode).
-If \verb|message| is \nil, the error handler is not called.
-Function \verb|error| never returns.
-\verb|error| is equivalent to the API function \verb|lua_error|.
+\subsubsection*{\ff \T{rawgetglobal (name)}}\Deffunc{rawgetglobal}
+Gets the value of a global variable,
+without invoking any tag method.
+The string \verb|name| does not need to be a
+syntactically valid variable name.
 
 \subsubsection*{\ff \T{rawgettable (table, index)}}\Deffunc{rawgettable}
 Gets the real value of \verb|table[index]|,
@@ -2293,6 +2528,15 @@ without invoking any tag method.
 \verb|table| must be a table,
 and \verb|index| is any value different from \nil.
 
+\subsubsection*{\ff \T{rawsetglobal (name, value)}}\Deffunc{rawsetglobal}
+Sets the named global variable to the given value,
+without invoking any tag method.
+The string \verb|name| does not need to be a
+syntactically valid variable name.
+Therefore,
+this function can be used to set global variables with strange names like
+\verb|"m v 1"| or \verb|"34"|.
+
 \subsubsection*{\ff \T{rawsettable (table, index, value)}}\Deffunc{rawsettable}
 Sets the real value of \verb|table[index]| to \verb|value|,
 without invoking any tag method.
@@ -2300,142 +2544,67 @@ without invoking any tag method.
 \verb|index| is any value different from \nil,
 and \verb|value| is any Lua value.
 
-\subsubsection*{\ff \T{rawsetglobal (name, value)}}\Deffunc{rawsetglobal}
-Assigns the given value to a global variable.
-The string \verb|name| does not need to be a
-syntactically valid variable name.
-Therefore,
-this function can set global variables with strange names like
-\verb|"m v 1"| or \verb|34|.
-
 \subsubsection*{\ff \T{setglobal (name, value)}}\Deffunc{setglobal}
-Assigns the given value to a global variable,
-or calls a tag method.
+Sets the named global variable to the given value,
+or calls a tag method for ``setgloball''.
 Its full semantics is explained in \See{tag-method}.
 The string \verb|name| does not need to be a
 syntactically valid variable name.
 
-\subsubsection*{\ff \T{rawgetglobal (name)}}\Deffunc{rawgetglobal}
-Retrieves the value of a global variable.
-The string \verb|name| does not need to be a
-syntactically valid variable name.
-
-\subsubsection*{\ff \T{getglobal (name)}}\Deffunc{getglobal}
-Retrieves the value of a global variable,
-or calls a tag method.
-Its full semantics is explained in \See{tag-method}.
-The string \verb|name| does not need to be a
-syntactically valid variable name.
+\subsubsection*{\ff \T{settag (t, tag)}}\Deffunc{settag}
+Sets the tag of a given table \see{TypesSec}.
+\verb|tag| must be a value created with \verb|newtag|
+\see{pdf-newtag}.
+It returns the value of its first argument (the table).
+For the safety of host programs,
+it is impossible to change the tag of a userdata from Lua.
 
 \subsubsection*{\ff \T{settagmethod (tag, event, newmethod)}}
 \Deffunc{settagmethod}
 Sets a new tag method to the given pair \M{(tag, event)}.
 It returns the old method.
 If \verb|newmethod| is \nil,
-\verb|settagmethod| restores the default behavior for the given event.
-
-\subsubsection*{\ff \T{gettagmethod (tag, event)}}
-\Deffunc{gettagmethod}
-Returns the current tag method
-for a given pair \M{(tag, event)}.
-
-\subsubsection*{\ff \T{copytagmethods (tagto, tagfrom)}}
-\Deffunc{copytagmethods}
-Copies all tag methods from one tag to another;
-it returns \verb|tagto|.
+then \verb|settagmethod| restores the default behavior for the given event.
 
-\subsubsection*{\ff \T{getn (table)}}\Deffunc{getn}\label{getn}
-Returns the ``size'' of a table, when seen as a list.
-If the table has an \verb|n| field with a numeric value,
-this is its ``size''.
-Otherwise, the size is the largest numerical index with a non-nil
-value in the table.
-This function could be defined in Lua:
-\begin{verbatim}
-      function getn (t)
-        if type(t.n) == 'number' then return t.n end
-        local max, i = 0, nil
-        while 1 do
-          i = next(t, i)
-          if not i then break end
-          if type(i) == 'number' and i>max then max=i end
-        end
-        return max
-      end
-\end{verbatim}
-
-
-\subsubsection*{\ff \T{foreach (table, function)}}\Deffunc{foreach}
-Executes the given \verb|function| over all elements of \verb|table|.
-For each element, the function is called with the index and
-respective value as arguments.
-If the function returns any non-\nil\ value,
-the loop is broken, and the value is returned
-as the final value of \verb|foreach|.
-
-This function could be defined in Lua:
-\begin{verbatim}
-      function foreach (t, f)
-        local i, v = nil
-        while 1 do
-          i, v = next(t, i)
-          if not i then break end
-          local res = f(i, v)
-          if res then return res end
-        end
-      end
-\end{verbatim}
+\subsubsection*{\ff \T{sort (table [, comp])}}\Deffunc{sort}
+Sorts table elements in a given order, \emph{in-place},
+from \verb|table[1]| to \verb|table[n]|,
+where \verb|n| is the result of \verb|getn(table)| \see{getn}.
+If \verb|comp| is given,
+it must be a function that receives two table elements,
+and returns true when the first is less than the second
+(so that \verb|not comp(a[i+1], a[i])| will be true after the sort).
+If \verb|comp| is not given,
+the standard Lua operator \verb|<| is used instead.
 
-If you create new indices in a table while
-traversing it,
-the semantics of \verb|foreach| is undefined.
+\subsubsection*{\ff \T{tag (v)}}\Deffunc{tag}\label{pdf-tag}
+Allows Lua programs to test the tag of a value \see{TypesSec}.
+It receives one argument, and returns its tag (a number).
+\verb|tag| is equivalent to the API function \verb|lua_tag|.
 
+\subsubsection*{\ff \T{tonumber (e [, base])}}\Deffunc{tonumber}
+Receives one argument,
+and tries to convert it to a number.
+If the argument is already a number or a string convertible
+to a number, then \verb|tonumber| returns that number;
+otherwise, it returns \nil.
 
-\subsubsection*{\ff \T{foreachi (table, function)}}\Deffunc{foreachi}
-Executes the given \verb|function| over the
-numerical indices of \verb|table|.
-For each index, the function is called with the index and
-respective value as arguments.
-Indices are visited in sequential order,
-from 1 to \verb|n|,
-where \verb|n| is the result of \verb|getn(table)| \see{getn}.
-If the function returns any non-\nil\ value,
-the loop is broken, and the value is returned
-as the final value of \verb|foreachi|.
+An optional argument specifies the base to interpret the numeral.
+The base may be any integer between 2 and 36, inclusive.
+In bases above~10, the letter `A' (either upper or lower case)
+represents~10, `B' represents~11, and so forth, with `Z' representing 35.
 
-This function could be defined in Lua:
-\begin{verbatim}
-      function foreachi (t, f)
-        for i=1,getn(t) do
-          local res = f(i, t[i])
-          if res then return res end
-        end
-      end
-\end{verbatim}
+In base 10 (the default), the number may have a decimal part,
+as well as an optional exponent part \see{coercion}.
+In other bases, only unsigned integers are accepted.
 
-\subsubsection*{\ff \T{foreachvar (function)}}\Deffunc{foreachvar}
-Executes \verb|function| over all global variables.
-For each variable,
-the function is called with its name and its value as arguments.
-If the function returns any non-nil value,
-the loop is broken, and the value is returned
-as the final value of \verb|foreachvar|.
+\subsubsection*{\ff \T{tostring (e)}}\Deffunc{tostring}
+Receives an argument of any type and
+converts it to a string in a reasonable format.
+For complete control on how numbers are converted,
+use function \verb|format|.
 
-This function could be defined in Lua:
-\begin{verbatim}
-      function foreachvar (f)
-        local n, v = nil
-        while 1 do
-          n, v = nextvar(n)
-          if not n then break end
-          local res = f(n, v)
-          if res then return res end
-        end
-      end
-\end{verbatim}
 
-If you create new global variables during the traversal,
-the semantics of \verb|foreachvar| is undefined.
 
 \subsubsection*{\ff \T{tinsert (table [, pos] , value)}}\Deffunc{tinsert}
 
@@ -2445,12 +2614,11 @@ The default value for \verb|pos| is \verb|n+1|,
 where \verb|n| is the result of \verb|getn(table)| \see{getn},
 so that a call \verb|tinsert(t,x)| inserts \verb|x| at the end
 of table \verb|t|.
-
-This function also sets or increments the field \verb|n| of the table,
+This function also sets or increments the field \verb|n| of the table
 to \verb|n+1|.
 
 This function is equivalent to the following Lua function,
-except that the table accesses are all raw (that is, without tag methods):
+except that the table accesses are all \emph{raw} (that is, without tag methods):
 \begin{verbatim}
       function tinsert (t, ...)
         local pos, value
@@ -2473,16 +2641,15 @@ except that the table accesses are all raw (that is, without tag methods):
 Removes from \verb|table| the element at position \verb|pos|,
 shifting other elements to close the space, if necessary.
 Returns the value of the removed element.
-The default value for \verb|pos| is \verb|n|
-(where \verb|n| is the result of \verb|getn(table)| \see{getn}),
+The default value for \verb|pos| is \verb|n|,
+where \verb|n| is the result of \verb|getn(table)| \see{getn},
 so that a call \verb|tremove(t)| removes the last element
 of table \verb|t|.
-
-This function also sets or decrements the field \verb|n| of the table,
+This function also sets or decrements the field \verb|n| of the table
 to \verb|n-1|.
 
 This function is equivalent to the following Lua function,
-except that the table accesses are all raw (that is, without tag methods):
+except that the table accesses are all \emph{raw} (that is, without tag methods):
 \begin{verbatim}
       function tremove (t, pos)
         local n = getn(t)
@@ -2498,16 +2665,17 @@ except that the table accesses are all raw (that is, without tag methods):
       end
 \end{verbatim}
 
-\subsubsection*{\ff \T{sort (table [, comp])}}\Deffunc{sort}
-Sorts table elements in a given order, \emph{in-place},
-from \verb|table[1]| to \verb|table[n]|,
-where \verb|n| is the result of \verb|getn(table)| \see{getn}.
-If \verb|comp| is given,
-it must be a function that receives two table elements,
-and returns true when the first is less than the second
-(so that \verb|not comp(a[i+1], a[i])| will be true after the sort).
-If \verb|comp| is not given,
-the standard Lua operator \verb|<| is used instead.
+\subsubsection*{\ff \T{type (v)}}\Deffunc{type}\label{pdf-type}
+Allows Lua programs to test the type of a value.
+It receives one argument, and returns its type, coded as a string.
+The possible results of this function are
+\verb|"nil"| (a string, not the value \nil),
+\verb|"number"|,
+\verb|"string"|,
+\verb|"table"|,
+\verb|"function"|,
+and \verb|"userdata"|.
+\verb|type| is equivalent to the API function \verb|lua_type|.
 
 
 \subsection{String Manipulation}
@@ -2516,6 +2684,26 @@ such as finding and extracting substrings and pattern matching.
 When indexing a string, the first character is at position~1
 (not at~0, as in C).
 
+\subsubsection*{\ff \T{strbyte (s [, i])}}\Deffunc{strbyte}
+Returns the internal numerical code of the character \verb|s[i]|.
+If \verb|i| is absent, then it is assumed to be 1.
+If \verb|i| is negative,
+it is replaced by the length of the string minus its
+absolute value plus 1.
+Therefore, \Math{-1} points to the last character of \verb|s|.
+
+\NOTE
+\emph{numerical codes are not necessarily portable across platforms}.
+
+\subsubsection*{\ff \T{strchar (i1, i2, \ldots)}}\Deffunc{strchar}
+Receives 0 or more integers.
+Returns a string with length equal to the number of arguments,
+wherein each character has the internal numerical code equal
+to its correspondent argument.
+
+\NOTE
+\emph{numerical codes are not necessarily portable across platforms}.
+
 \subsubsection*{\ff \T{strfind (str, pattern [, init [, plain]])}}
 \Deffunc{strfind}
 Looks for the first \emph{match} of
@@ -2523,7 +2711,7 @@ Looks for the first \emph{match} of
 If it finds one, then it returns the indices on \verb|str|
 where this occurrence starts and ends;
 otherwise, it returns \nil.
-If the pattern specifies captures,
+If the pattern specifies captures (see \verb|gsub| below),
 the captured strings are returned as extra results.
 A third optional numerical argument specifies where to start the search;
 its default value is 1.
@@ -2538,6 +2726,19 @@ with no characters in \verb|pattern| being considered ``magic''.
 
 \subsubsection*{\ff \T{strlen (s)}}\Deffunc{strlen}
 Receives a string and returns its length.
+The empty string \verb|""| has length 0.
+Embedded zeros are counted.
+
+\subsubsection*{\ff \T{strlower (s)}}\Deffunc{strlower}
+Receives a string and returns a copy of that string with all
+upper case letters changed to lower case.
+All other characters are left unchanged.
+The definition of what is an upper-case
+letter depends on the current locale.
+
+\subsubsection*{\ff \T{strrep (s, n)}}\Deffunc{strrep}
+Returns a string that is the concatenation of \verb|n| copies of
+the string \verb|s|.
 
 \subsubsection*{\ff \T{strsub (s, i [, j])}}\Deffunc{strsub}
 Returns another string, which is a substring of \verb|s|,
@@ -2555,13 +2756,6 @@ with length \verb|j|,
 and the call \verb|strsub(s, -i)| returns a suffix of \verb|s|
 with length \verb|i|.
 
-\subsubsection*{\ff \T{strlower (s)}}\Deffunc{strlower}
-Receives a string and returns a copy of that string with all
-upper case letters changed to lower case.
-All other characters are left unchanged.
-The definition of what is an upper case
-letter depends on the current locale.
-
 \subsubsection*{\ff \T{strupper (s)}}\Deffunc{strupper}
 Receives a string and returns a copy of that string with all
 lower case letters changed to upper case.
@@ -2569,42 +2763,20 @@ All other characters are left unchanged.
 The definition of what is a lower case
 letter depends on the current locale.
 
-\subsubsection*{\ff \T{strrep (s, n)}}\Deffunc{strrep}
-Returns a string that is the concatenation of \verb|n| copies of
-the string \verb|s|.
-
-\subsubsection*{\ff \T{strbyte (s [, i])}}\Deffunc{strbyte}
-Returns the internal numerical code of the character \verb|s[i]|.
-If \verb|i| is absent, then it is assumed to be 1.
-If \verb|i| is negative,
-it is replaced by the length of the string minus its
-absolute value plus 1.
-Therefore, \Math{-1} points to the last character of \verb|s|.
-
-Note that numerical codes are not necessarily portable across platforms.
-
-\subsubsection*{\ff \T{strchar (i1, i2, \ldots)}}\Deffunc{strchar}
-Receives 0 or more integers.
-Returns a string with length equal to the number of arguments,
-wherein each character has the internal numerical code equal
-to its correspondent argument.
-
-Note that numerical codes are not necessarily portable across platforms.
-
 \subsubsection*{\ff \T{format (formatstring, e1, e2, \ldots)}}\Deffunc{format}
 \label{format}
 Returns a formatted version of its variable number of arguments
 following the description given in its first argument (which must be a string).
 The format string follows the same rules as the \verb|printf| family of
-standard C functions.
+standard C~functions.
 The only differences are that the options/modifiers
 \verb|*|, \verb|l|, \verb|L|, \verb|n|, \verb|p|,
 and \verb|h| are not supported,
 and there is an extra option, \verb|q|.
-This option formats a string in a form suitable to be safely read
+The \verb|q| option formats a string in a form suitable to be safely read
 back by the Lua interpreter:
 The string is written between double quotes,
-and all double quotes, returns and backslashes in the string
+and all double quotes, returns, and backslashes in the string
 are correctly escaped when written.
 For instance, the call
 \begin{verbatim}
@@ -2616,7 +2788,7 @@ will produce the string:
  new line"
 \end{verbatim}
 
-Conversions can be applied to the n-th argument in the argument list,
+Conversions can be applied to the \M{n}-th argument in the argument list,
 rather than the next unused argument.
 In this case, the conversion character \verb|%| is replaced
 by the sequence \verb|%d$|, where \verb|d| is a
@@ -2635,13 +2807,14 @@ the appropriate format string.
 For example, \verb|"%*g"| can be simulated with
 \verb|"%"..width.."g"|.
 
-\emph{Note: function \T{format} can only be used with strings that do not
-contain zeros (0).}
+\NOTE
+\emph{Neither the format string nor the string values to be formatted with
+\T{format} can contain embedded zeros.}
 
 \subsubsection*{\ff \T{gsub (s, pat, repl [, n])}}
 \Deffunc{gsub}
 Returns a copy of \verb|s|,
-where all occurrences of the pattern \verb|pat| have been
+in which all occurrences of the pattern \verb|pat| have been
 replaced by a replacement string specified by \verb|repl|.
 This function also returns, as a second value,
 the total number of substitutions made.
@@ -2649,7 +2822,7 @@ the total number of substitutions made.
 If \verb|repl| is a string, then its value is used for replacement.
 Any sequence in \verb|repl| of the form \verb|%n|
 with \verb|n| between 1 and 9
-stands for the value of the n-th captured substring.
+stands for the value of the \M{n}-th captured substring.
 
 If \verb|repl| is a function, then this function is called every time a
 match occurs, with all captured substrings passed as arguments,
@@ -2658,7 +2831,7 @@ If the value returned by this function is a string,
 then it is used as the replacement string;
 otherwise, the replacement string is the empty string.
 
-A last optional parameter \verb|n| limits
+The last, optional parameter \verb|n| limits
 the maximum number of substitutions to occur.
 For instance, when \verb|n| is 1 only the first occurrence of
 \verb|pat| is replaced.
@@ -2713,18 +2886,19 @@ The following combinations are allowed in describing a character class:
 \item[\T{\%\M{x}}] (where \M{x} is any non alphanumeric character)  ---
 represents the character \M{x}.
 This is the standard way to escape the magic characters \verb|()%.[]*-?|.
-It is strongly recommended that any control character (even the non magic),
-when used to represent itself in a pattern, should be preceded by a \verb|%|.
+It is strongly recommended that any control character (even the non magic)
+should be preceded by a \verb|%|
+when used to represent itself in a pattern,
 
 \item[\T{[char-set]}] ---
-Represents the class which is the union of all
+represents the class which is the union of all
 characters in char-set.
 A range of characters may be specified by
 separating the end characters of the range with a \verb|-|.
-All classes \verb|%|\emph{x} described above can also be used as
+All classes \verb|%|\emph{x} described above may also be used as
 components in a char-set.
 All other characters in char-set represent themselves.
-E.g., \verb|[%w_]| (or \verb|[_%w]|)
+For example, \verb|[%w_]| (or \verb|[_%w]|)
 represents all alphanumeric characters plus the underscore,
 \verb|[0-7]| represents the octal digits,
 and \verb|[0-7%l%-]| represents the octal digits plus
@@ -2739,7 +2913,7 @@ represents the complement of char-set,
 where char-set is interpreted as above.
 \end{description}
 For all classes represented by single letters (\verb|%a|, \verb|%c|, \ldots),
-the correspondent upper-case letter represents the complement of the class.
+the corresponding upper-case letter represents the complement of the class.
 For instance, \verb|%S| represents all non-space characters.
 
 The definitions of letter, space, etc. depend on the current locale.
@@ -2770,14 +2944,14 @@ a single character class followed by \verb|?|,
 which matches 0 or 1 occurrence of a character in the class;
 \item
 \T{\%\M{n}}, for \M{n} between 1 and 9;
-such item matches a sub-string equal to the n-th captured string
+such item matches a sub-string equal to the \M{n}-th captured string
 (see below);
 \item
 \T{\%b\M{xy}}, where \M{x} and \M{y} are two distinct characters;
-such item matches strings that start with \M{x}, end with \M{y},
+such item matches strings that start with~\M{x}, end with~\M{y},
 and where the \M{x} and \M{y} are \emph{balanced}.
-That means that, if one reads the string from left to write,
-counting plus 1 for an \M{x} and minus 1 for a \M{y},
+This means that, if one reads the string from left to right,
+counting \Math{+1} for an \M{x} and \Math{-1} for a \M{y},
 the ending \M{y} is the first where the count reaches 0.
 For instance, the item \verb|%b()| matches expressions with
 balanced parentheses.
@@ -2789,9 +2963,11 @@ A \verb|^| at the beginning of a pattern anchors the match at the
 beginning of the subject string.
 A \verb|$| at the end of a pattern anchors the match at the
 end of the subject string.
+At other positions,
+\verb|^| and \verb|$| have no special meaning and represent themselves.
 
 \paragraph{Captures:}
-a pattern may contain sub-patterns enclosed in parentheses,
+A pattern may contain sub-patterns enclosed in parentheses,
 that describe \Def{captures}.
 When a match succeeds, the sub-strings of the subject string
 that match captures are stored (\emph{captured}) for future use.
@@ -2802,8 +2978,9 @@ stored as the first capture (and therefore has number~1);
 the character matching \verb|.| is captured with number~2,
 and the part matching \verb|%s*| has number~3.
 
-{\em Note: A pattern cannot contain zeros (\verb|'\0'|).
-Use \verb|'%z'| instead.}
+\NOTE
+{\em A pattern cannot contain embedded zeros.
+Use \verb|%z| instead.}
 
 
 \subsection{Mathematical Functions} \label{mathlib}
@@ -2820,13 +2997,13 @@ The library provides the following functions:
 \Deffunc{frexp}\Deffunc{ldexp}
 \Deffunc{random}\Deffunc{randomseed}
 \begin{verbatim}
-abs acos asin atan atan2 ceil cos deg   floor log log10
-max min  mod  rad  sin   sqrt tan frexp ldexp
-random   randomseed
+   abs  acos  asin  atan  atan2  ceil  cos  deg     floor  log  log10
+   max  min   mod   rad   sin    sqrt  tan  frexp   ldexp
+   random     randomseed
 \end{verbatim}
 plus a global variable \IndexVerb{PI}.
 Most of them
-are only interfaces to the homonymous functions in the C library,
+are only interfaces to the homonymous functions in the C~library,
 except that, for the trigonometric functions,
 all angles are expressed in \emph{degrees}, not radians.
 Functions \IndexVerb{deg} and \IndexVerb{rad} can be used to convert
@@ -2835,11 +3012,12 @@ between radians and degrees.
 The function \verb|max| returns the maximum
 value of its numeric arguments.
 Similarly, \verb|min| computes the minimum.
-Both can be used with 1, 2 or more arguments.
+Both can be used with 1, 2, or more arguments.
 
 The functions \verb|random| and \verb|randomseed| are interfaces to
 the simple random generator functions \verb|rand| and \verb|srand|,
 provided by ANSI C.
+(No guarantees can be given for their statistical properties.)
 The function \verb|random|, when called without arguments,
 returns a pseudo-random real number in the range \Math{[0,1)}.
 When called with a number \Math{n},
@@ -2855,7 +3033,7 @@ over two \Def{file handles}, one for reading and one for writing.
 These handles are stored in two Lua global variables,
 called \verb|_INPUT| and \verb|_OUTPUT|.
 The global variables
-\verb|_STDIN|, \verb|_STDOUT| and \verb|_STDERR|
+\verb|_STDIN|, \verb|_STDOUT|, and \verb|_STDERR|
 are initialized with file descriptors for
 \verb|stdin|, \verb|stdout| and \verb|stderr|.
 Initially, \verb|_INPUT=_STDIN| and \verb|_OUTPUT=_STDOUT|.
@@ -2877,7 +3055,7 @@ It returns a new file handle,
 or, in case of errors, \nil\ plus a string describing the error.
 This function does not modify either \verb|_INPUT| or \verb|_OUTPUT|.
 
-The string mode can be any of the following:
+The \verb|mode| string can be any of the following:
 \begin{description}
 \item[``r''] read mode;
 \item[``w''] write mode;
@@ -2887,8 +3065,9 @@ The string mode can be any of the following:
 \item[``a+''] append update mode, previous data is preserved,
   writing is only allowed at the end of file.
 \end{description}
-The string mode may also have a \verb|b| at the end,
+The \verb|mode| string may also have a \verb|b| at the end,
 which is needed in some systems to open the file in binary mode.
+This string is exactlty what is used in the standard~C function \verb|fopen|.
 
 \subsubsection*{\ff \T{closefile (handle)}}\Deffunc{closefile}
 
@@ -2972,7 +3151,7 @@ plus a string describing the error.
 
 Saves any written data to the given file.
 If \verb|filehandle| is not specified,
-flushes all open files.
+then \verb|flush| flushes all open files.
 If this function fails, it returns \nil,
 plus a string describing the error.
 
@@ -3016,7 +3195,7 @@ according to the given formats, which specify what to read.
 For each format,
 the function returns a string (or a number) with the characters read,
 or \nil\ if it cannot read data with the specified format.
-When called without patterns,
+When called without formats,
 it uses a default format that reads the next line
 (see below).
 
@@ -3032,6 +3211,8 @@ On end of file, it returns the empty string.
 \item[``*w''] reads the next word
 (maximal sequence of non white-space characters),
 skipping spaces if necessary, or \nil\ on end of file.
+\item[\emph{number}] reads a string with up to that number of characters,
+or \nil\ on end of file.
 \end{description}
 
 \subsubsection*{\ff \T{write ([filehandle, ] value1, ...)}}\Deffunc{write}
@@ -3049,7 +3230,7 @@ plus a string describing the error.
 
 Returns a string containing date and time
 formatted according to the given string \verb|format|,
-following the same rules of the ANSI C function \verb|strftime|.
+following the same rules of the ANSI~C function \verb|strftime|.
 When called without arguments,
 it returns a reasonable date and time representation that depends on
 the host system and on the current locale.
@@ -3061,7 +3242,7 @@ used by the program, in seconds.
 
 \subsubsection*{\ff \T{exit ([code])}}\Deffunc{exit}
 
-Calls the C function \verb|exit|,
+Calls the C~function \verb|exit|,
 with an optional \verb|code|,
 to terminate the program.
 The default value for \verb|code| is the success code.
@@ -3073,13 +3254,13 @@ or \nil\ if the variable is not defined.
 
 \subsubsection*{\ff \T{execute (command)}}\Deffunc{execute}
 
-This function is equivalent to the C function \verb|system|.
+This function is equivalent to the C~function \verb|system|.
 It passes \verb|command| to be executed by an operating system shell.
 It returns a status code, which is system-dependent.
 
 \subsubsection*{\ff \T{setlocale (locale [, category])}}\Deffunc{setlocale}
 
-This function is an interface to the ANSI C function \verb|setlocale|.
+This function is an interface to the ANSI~C function \verb|setlocale|.
 \verb|locale| is a string specifying a locale;
 \verb|category| is an optional string describing which category to change:
 \verb|"all"|, \verb|"collate"|, \verb|"ctype"|,
@@ -3089,7 +3270,7 @@ The function returns the name of the new locale,
 or \nil\ if the request cannot be honored.
 
 
-\section{The Debugger Interface} \label{debugI}
+\section{The Debug Interface} \label{debugI}
 
 Lua has no built-in debugging facilities.
 Instead, it offers a special interface,
@@ -3097,7 +3278,8 @@ by means of functions and \emph{hooks},
 which allows the construction of different
 kinds of debuggers, profilers, and other tools
 that need ``inside information'' from the interpreter.
-This interface is declared in the header file \verb|luadebug.h|.
+This interface is declared in the header file \verb|luadebug.h|,
+and has \emph{no} single-state variant.
 
 \subsection{Stack and Function Information}
 
@@ -3106,23 +3288,24 @@ The main function to get information about the interpreter stack is
 \begin{verbatim}
 int lua_getstack (lua_State *L, int level, lua_Debug *ar);
 \end{verbatim}
-It fills parts of a structure (\verb|lua_Debug|) with
+It fills parts of a \verb|lua_Debug| structure with
 an identification of the \emph{activation record}
 of the function executing at a given level.
 Level~0 is the current running function,
-while level \Math{n+1} is the function that has called level \Math{n}.
+whereas level \Math{n+1} is the function that has called level \Math{n}.
 Usually, \verb|lua_getstack| returns 1;
 when called with a level greater than the stack depth,
 it returns 0.
 
-The structure \verb|lua_Debug| is used to carry different informations
-about an active function: \Deffunc{lua_Debug}
+\Deffunc{lua_Debug}
+The structure \verb|lua_Debug| is used to carry different pieces of information
+about an active function:
 \begin{verbatim}
 struct lua_Debug {
-  const char *event;     /* `call', `return' */
+  const char *event;     /* "call", "return" */
   const char *source;    /* (S) */
   int linedefined;       /* (S) */
-  const char *what;      /* (S) `Lua' function, `C' function, Lua `main' */
+  const char *what;      /* (S) "Lua" function, "C" function, Lua "main" */
   int currentline;       /* (l) */
   const char *name;      /* (n) */
   const char *namewhat;  /* (n) global, tag method, local, field */
@@ -3135,15 +3318,18 @@ struct lua_Debug {
 The \verb|lua_getstack| function fills only the private part
 of this structure, for future use.
 To fill in the other fields of \verb|lua_Debug| with useful information,
-you call \Deffunc{lua_getinfo}
+call \Deffunc{lua_getinfo}
 \begin{verbatim}
 int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);
 \end{verbatim}
-Each character in string \verb|what| selects some fields to be filled,
-as indicated by the letter in parentheses in the structure definition;
+This function returns 0 on error
+(e.g., an invalid option in \verb|what|).
+Each character in the string \verb|what|
+selects some fields of \verb|ar| to be filled,
+as indicated by the letter in parentheses in the definition of \verb|lua_Debug|;
 that is, an \verb|S| fills the fields \verb|source| and \verb|linedefined|,
 and \verb|l| fills the field \verb|currentline|, etc.
-Next we describe each field:
+We describe each field below:
 \begin{description}
 
 \item[source]
@@ -3156,7 +3342,7 @@ if the function was defined in a file,
 the line number where starts the definition of the function.
 
 \item[what] the string \verb|"Lua"| if this is a Lua function,
-\verb|"C"| if this is a C function,
+\verb|"C"| if this is a C~function,
 or \verb|"main"| if this is the main part of a chunk.
 
 \item[currentline]
@@ -3175,11 +3361,11 @@ while others may be stored only in a table field.
 The \verb|lua_getinfo| function checks whether the given
 function is a tag method or the value of a global variable.
 If the given function is a tag method,
-\verb|name| points to the event name.
+then \verb|name| points to the event name.
 If the given function is the value of a global variable,
-\verb|name| points to the variable name.
+then \verb|name| points to the variable name.
 If the given function is neither a tag method nor a global variable,
-\verb|name| is set to \verb|NULL|.
+then \verb|name| is set to \verb|NULL|.
 
 \item[namewhat]
 Explains the previous field.
@@ -3190,8 +3376,8 @@ if the function is a tag method,
 otherwise \verb|namewhat| is \verb|""| (the empty string).
 
 \item[nups]
-Number of upvalues of a C function.
-If the function is not a C function,
+Number of upvalues of a C~function.
+If the function is not a C~function,
 \verb|nups| is set to 0.
 
 \item[func]
@@ -3206,6 +3392,10 @@ int lua_setdebug (lua_State *L, int debug);
 \end{verbatim}
 This function sets the flag and returns its previous value.
 This flag can also be set from Lua~\see{pragma}.
+Setting the flag using \verb|lua_setdebug| affects all chunks that are
+compiled afterwards.
+Individual functions may still control the generation of debug information
+by using \verb|$debug| or \verb|$nodebug|.
 
 \subsection{Manipulating Local Variables}
 
@@ -3235,7 +3425,7 @@ int lua_setlocal (lua_State *L, const lua_Debug *ar, lua_Localvar *v);
 \end{verbatim}
 The parameter \verb|ar| must be a valid activation record,
 filled by a previous call to \verb|lua_getstack| or
-given as argument to a hook (see next section).
+given as argument to a hook \see{sub-hooks}.
 To use \verb|lua_getlocal|,
 you fill the \verb|index| field of \verb|v| with the index
 of a local variable; then the function fills the fields
@@ -3256,7 +3446,7 @@ int listvars (lua_State *L, int level) {
   int i;
   if (lua_getstack(L, level, &ar) == 0)
     return 0;  /* failure: no such level on the stack */
-  for (i=1; ;i++) {
+  for (i=1; ; i++) {
     lua_Localvar v;
     v.index = i;
     if (lua_getlocal(L, &ar, &v) == 0)
@@ -3267,7 +3457,7 @@ int listvars (lua_State *L, int level) {
 \end{verbatim}
 
 
-\subsection{Hooks}
+\subsection{Hooks}\label{sub-hooks}
 
 The Lua interpreter offers two hooks for debugging purposes:
 a \emph{call} hook and a \emph{line} hook.
@@ -3297,8 +3487,9 @@ local variables.
 
 The line hook is called every time the interpreter changes
 the line of code it is executing.
-The \verb|currentline| field of \verb|ar| has the line number.
-Again, you can use this \verb|ar| in other calls to the API.
+The \verb|event| field of \verb|ar| has the string \verb|"line"|,
+and the \verb|currentline| field has the line number.
+Again, you can use this \verb|ar| in other calls to the debug API.
 This hook is called only if the active function
 has been compiled with debug information~\see{pragma}.
 
@@ -3313,10 +3504,10 @@ called by the hook, because those errors are protected;
 the control returns to the hook anyway.)
 
 
-\subsection{The Reflexive Debugger Interface}
+\subsection{The Reflexive Debug Interface}
 
 The library \verb|ldblib| provides
-the functionality of the debugger interface to Lua programs.
+the functionality of the debug interface to Lua programs.
 If you want to use this library,
 your host application must open it,
 by calling \verb|lua_dblibopen|.
@@ -3332,9 +3523,9 @@ As a general rule, if your program does not need this library,
 do not open it.
 
 
-\subsubsection*{\ff \T{getstack (level, what)}}\Deffunc{getstack}
+\subsubsection*{\ff \T{getstack (level, [what])}}\Deffunc{getstack}
 
-This function returns a table with informations about the function
+This function returns a table with information about the function
 running at level \verb|level| of the stack.
 Level 0 is the current function (\verb|getstack| itself);
 level 1 is the function that called \verb|getstack|.
@@ -3342,9 +3533,11 @@ If \verb|level| is larger than the number of active functions,
 the function returns \nil.
 The table contains all the fields returned by \verb|lua_getinfo|,
 with the string \verb|what| describing what to get.
+The default for \rerb|what| is to get all information available.
 
-For instance, the expression \verb|getstack(1, 'n').name| returns
-the name of the current function.
+For instance, the expression \verb|getstack(1,"n").name| returns
+the name of the current function,
+if a reasonable name can be found.
 
 
 \subsubsection*{\ff \T{getlocal (level, local)}}\Deffunc{getlocal}
@@ -3402,11 +3595,13 @@ the language is frequently used as a stand-alone interpreter.
 An implementation of such an interpreter,
 called simply \verb|lua|,
 is provided with the standard distribution.
+
 This program can be called with any sequence of the following arguments:
 \begin{description}
 \item[\T{-}] executes \verb|stdin| as a file;
+\item[\T{-c}] calls \verb|lua_close| after running all arguments;
 \item[\T{-d}] turns on debug information;
-\item[\T{-e stat}] executes string \verb|stat|;
+\item[\T{-e} \rm\emph{stat}] executes string \verb|stat|;
 \item[\T{-f filename}] executes file \verb|filename| with the
 remaining arguments in table \verb|arg|;
 \item[\T{-i}] enters interactive mode with prompt;
@@ -3424,7 +3619,7 @@ For instance, an invocation like
 \begin{verbatim}
 $ lua -i a=test prog.lua
 \end{verbatim}
-will first interact with the user until an \verb|EOF|,
+will first interact with the user until an \verb|EOF| in \verb|stdin|,
 then will set \verb|a| to \verb|"test"|,
 and finally will run the file \verb|prog.lua|.
 
@@ -3443,19 +3638,21 @@ then creates a table \T{arg},
   arg = {"t1", "t3";  n = 2, [0] = "b.lua"}
 \end{verbatim}
 and then runs the file \T{b.lua}.
+The stand-alone interpreter also provides a \verb|getarg| function that
+can be used to access \emph{all} command line arguments.
 
 In interactive mode,
 a multi-line statement can be written finishing intermediate
 lines with a backslash (\verb|\|).
 If the global variable \verb|_PROMPT| is defined as a string,
-its value is used as the prompt. \Index{_PROMPT}
+its value is used as the prompt. \index{_PROMPT}
 Therefore, the prompt can be changed like below:
 \begin{verbatim}
 $ lua _PROMPT='myprompt> ' -i
 \end{verbatim}
 
 In Unix systems, Lua scripts can be made into executable programs
-by using the \verb|#!| form,
+by using \verb|chmod +x| and the~\verb|#!| form,
 as in \verb|#!/usr/local/bin/lua|,
 or \verb|#!/usr/local/bin/lua -f| to get other arguments.
 
@@ -3470,7 +3667,6 @@ who found the name of the game.
 Lua means \emph{moon} in Portuguese.
 
 
-
 \appendix
 
 \section*{Incompatibilities with Previous Versions}
@@ -3482,12 +3678,154 @@ Here is a list of all these incompatibilities.
 
 \subsection*{Incompatibilities with \Index{version 3.2}}
 \begin{itemize}
-\item
 
+\item
+General read patterns are now deprecated.
+\item
+Garbage-collection tag methods for tables is now deprecated.
+\item
+\verb|setglobal|, \verb|rawsetglobal|, and \verb|sort| no longer return a value;
+\verb|type| no longer return a second value.
+\item
+In nested function calls like \verb|f(g(x))|
+\emph{all} return values from \verb|g| are passed as arguments to \verb|f|.
+(This only happens when \verb|g| is the last
+[or the only] argument to \verb|f|.)
+\item
+There is now only one tag method for order operators.
+\item
+The debug API has been completely rewritten.
+\item
+The pre-compiler may use the fact that some operators are associative,
+for optimizations.
+This may cause problems if these operators
+have non-associative tag methods.
+\item
+All functions from the old API are now macros.
+\item
+A \verb|const| qualifier has been added to \verb|char *|
+in all API functions that handle C~strings.
+\item
+\verb|luaL_openlib| no longer automatically calls \verb|lua_open|.
+So,
+you must now explicitly call \verb|lua_open| before opening
+the standard libraries.
+\item
+\verb|lua_type| now returns a string describing the type,
+and is no longer a synonym for \verb|lua_tag|.
 \item Old pre-compiled code is obsolete, and must be re-compiled.
 
 \end{itemize}
 
+%{===============================================================
+\section*{The complete syntax of Lua}
+
+\renewenvironment{Produc}{\vspace{0.8ex}\par\noindent\hspace{3ex}\it\begin{tabular}{rrl}}{\end{tabular}\vspace{0.8ex}\par\noindent}
+
+\renewcommand{\OrNL}{\\ & \Or & }
+
+\begin{Produc}
+
+\produc{chunk}{\rep{stat} \opt{ret}}
+
+\produc{block}{\opt{label} \rep{stat \opt{\ter{;}}}}
+
+\produc{label}{\ter{$\vert$} name \ter{$\vert$}}
+
+\produc{stat}{%
+	varlist1 \ter{=} explist1
+\OrNL	functioncall
+\OrNL	\rwd{do} block \rwd{end}
+\OrNL	\rwd{while} exp1 \rwd{do} block \rwd{end}
+\OrNL	\rwd{repeat} block \rwd{until} exp1
+\OrNL	\rwd{if} exp1 \rwd{then} block
+	\rep{\rwd{elseif} exp1 \rwd{then} block}
+	\opt{\rwd{else} block} \rwd{end}
+\OrNL	\rwd{return} \opt{explist1}
+\OrNL	\rwd{break} \opt{name}
+\OrNL	\rwd{for} name \ter{=} exp1 \ter{,} exp1 \opt{\ter{,} exp1}
+	\rwd{do} block \rwd{end}
+\OrNL	\rwd{function} funcname \ter{(} \opt{parlist1} \ter{)} block \rwd{end}
+\OrNL	\rwd{local} declist \opt{init}
+}
+
+\produc{var}{%
+	name
+\OrNL	simpleexp \ter{[} exp1 \ter{]}
+\OrNL	simpleexp \ter{.} name
+}
+
+\produc{varlist1}{var \rep{\ter{,} var}}
+
+\produc{declist}{name \rep{\ter{,} name}}
+
+\produc{init}{\ter{=} explist1}
+
+\produc{exp}{%
+	\rwd{nil}
+\Or	number
+\Or	literal
+\Or	function
+\Or	simpleexp
+\Or	\ter{(} exp \ter{)}
+}
+
+\produc{exp1}{exp}
+
+\produc{explist1}{\rep{exp1 \ter{,}} exp}
+
+\produc{simpleexp}{%
+	var
+\Or	upvalue
+\Or	functioncall
+\Or	tableconstructor
+}
+
+\produc{tableconstructor}{\ter{\{} fieldlist \ter{\}}}
+\produc{fieldlist}{%
+	lfieldlist
+\Or	ffieldlist
+\Or	lfieldlist \ter{;} ffieldlist
+\Or	ffieldlist \ter{;} lfieldlist
+}
+\produc{lfieldlist}{\opt{lfieldlist1}}
+\produc{ffieldlist}{\opt{ffieldlist1}}
+\produc{lfieldlist1}{exp \rep{\ter{,} exp} \opt{\ter{,}}}
+\produc{ffieldlist1}{ffield \rep{\ter{,} ffield} \opt{\ter{,}}}
+\produc{ffield}{%
+	\ter{[} exp \ter{]} \ter{=} exp
+\Or	name \ter{=} exp
+}
+
+\produc{functioncall}{%
+	simpleexp args
+\Or	simpleexp \ter{:} name args
+}
+
+\produc{args}{%
+	\ter{(} \opt{explist1} \ter{)}
+\Or	tableconstructor
+\Or	\ter{literal}
+}
+
+\produc{function}{\rwd{function} \ter{(} \opt{parlist1} \ter{)} block \rwd{end}}
+
+\produc{funcname}{%
+	name
+\OrNL	name \ter{.} name
+\OrNL	name \ter{:} name
+}
+
+\produc{parlist1}{%
+	\ter{\ldots}
+\Or	name \rep{\ter{,} name} \opt{\ter{,} \ter{\ldots}}
+}
+
+\produc{upvalue}{\ter{\%} name}
+
+\end{Produc}
+%}===============================================================
+
 % restore underscore to usual meaning
 \catcode`\_=8
 
@@ -3498,5 +3836,3 @@ Here is a list of all these incompatibilities.
 
 
 \end{document}
-
-
-- 
cgit v1.2.3-55-g6feb

