Lua Grammar

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Lua 5.1 Grammar for Antlr

Lua 5.1 Grammar in the Reference Manual

"Section 8 - The Complete Syntax of Lua" of the Lua Reference Manual[1] provides an extended BNF grammar (without operator precedences) of Lua 5.1. For precedence, see [Section 2.5.6 - Precedence].

Lua 5.1 Grammar in Lemon format

This is essentially the same as Lemon[2] format, except that it permits quoted strings for literal terminals

%fallback  OPEN '(' .

chunk      ::= block .

semi       ::= ';' .
semi       ::= .

block      ::= scope statlist .
block      ::= scope statlist laststat semi .
ublock     ::= block 'until' exp .

scope      ::= .
scope      ::= scope statlist binding semi.
           
statlist   ::= .
statlist   ::= statlist stat semi .

stat       ::= 'do' block 'end' .
stat       ::= 'while' exp 'do' block 'end' .
stat       ::= repetition 'do' block 'end' .
stat       ::= 'repeat' ublock .
stat       ::= 'if' conds 'end' .
stat       ::= 'function' funcname funcbody .
stat       ::= setlist '=' explist1 .
stat       ::= functioncall .

repetition ::= 'for' NAME '=' explist23 .
repetition ::= 'for' namelist 'in' explist1 .
           
conds      ::= condlist .
conds      ::= condlist 'else' block .
condlist   ::= cond .
condlist   ::= condlist 'elseif' cond .
cond       ::= exp 'then' block .
           
laststat   ::= 'break' .
laststat   ::= 'return' .
laststat   ::= 'return' explist1 .

binding    ::= 'local' namelist .
binding    ::= 'local' namelist '=' explist1 .
binding    ::= 'local' 'function' NAME funcbody .

funcname   ::= dottedname .
funcname   ::= dottedname ':' NAME .

dottedname ::= NAME .
dottedname ::= dottedname '.' NAME .

namelist   ::= NAME .
namelist   ::= namelist ',' NAME .

explist1   ::= exp .
explist1   ::= explist1 ',' exp .
explist23  ::= exp ',' exp .
explist23  ::= exp ',' exp ',' exp .

%left      'or' .
%left      'and' .
%left      '<' '<=' '>' '>=' '==' '~=' .
%right     '..' .
%left      '+' '-' .
%left      '*' '/' '%' .
%right     'not' '#' .
%right     '^' .

exp        ::= 'nil'|'true'|'false'|NUMBER|STRING|'...' .
exp        ::= function .
exp        ::= prefixexp .
exp        ::= tableconstructor .
exp        ::= 'not'|'#'|'-' exp .         ['not']
exp        ::= exp 'or' exp .
exp        ::= exp 'and' exp .
exp        ::= exp '<'|'<='|'>'|'>='|'=='|'~=' exp .
exp        ::= exp '..' exp .
exp        ::= exp '+'|'-' exp .
exp        ::= exp '*'|'/'|'%' exp .
exp        ::= exp '^' exp .
           
setlist    ::= var .
setlist    ::= setlist ',' var .

var        ::= NAME .
var        ::= prefixexp '[' exp ']' .
var        ::= prefixexp '.' NAME .

prefixexp  ::= var .
prefixexp  ::= functioncall .
prefixexp  ::= OPEN exp ')' .

functioncall ::= prefixexp args .
functioncall ::= prefixexp ':' NAME args .

args        ::= '(' ')' .
args        ::= '(' explist1 ')' .
args        ::= tableconstructor .
args        ::= STRING .

function    ::= 'function' funcbody .

funcbody    ::= params block 'end' .

params      ::= '(' parlist ')' .

parlist     ::= .
parlist     ::= namelist .
parlist     ::= '...' .
parlist     ::= namelist ',' '...' .

tableconstructor ::= '{' '}' .
tableconstructor ::= '{' fieldlist '}' .
tableconstructor ::= '{' fieldlist ','|';' '}' .

fieldlist   ::= field .
fieldlist   ::= fieldlist ','|';' field .
            
field       ::= exp .
field       ::= NAME '=' exp .
field       ::= '[' exp ']' '=' exp .

--RiciLake

Lua 5.1/5.0 Compiler in C

The original C parser of Lua, of course, exists in the source code of the Lua distribution, but it is hand-written in C and not easy to reuse.

Lua 5.1 Lexer and Parser in LPeg in Lua

LpegRecipes lists a Lua 5.1 lexer and parser in Lua LPeg.

Lua 5.1 Parser in Lua

Cheese[3] is a parser generator that uses Parsing Expression Grammars (PEG) as its description formalism and Lua itself as a description language for the parsers. It includes a parser that understands the complete syntax of Lua 5.1. (The PEG appears to be an effort that predates LPeg.)

Lua 5.1 Compiler in Lua

[Yueliang] implements a full Lua compiler in Lua. It is a fairly direct port of the Lua C code to Lua.

Lua 5.1 Compiler in Parrot

Parrot [4] contains a compiler, written in Perl5, that compiles Lua 5.1 down to Parrot VM bytecodes (though it's a work in progress). There is also a web interface to the subversion repository [5].

See also related efforts:

• [Monkey] - an implementation of Lua on Parrot - A Lua to PIR compiler implemented in C
• [lua2pir] - A Lua bytecode to PIR compiler

Lua 5.1/5.0 Test Suite

Those reimplementing Lua may be interested in the test suite for 5.1 LuaList:2006-03/msg00716.html and 5.0 LuaList:2005-12/msg00312.html.

Lua 5.0 Parser in Lua - LuaParse

In August 2004, Rici Lake announced a new Lua 5.0 parser on the lua mailing list, implemented in Lua: [LuaParse].

A Lua 5.0 Grammar in Gentle

[Lua2js] contains a complete grammar for Lua 5.0 done with the Gentle[6] compiler construction kit.

Lua 5.0 in Parser in Haskell/Parsec

The lua-xgettext tool includes a parser in Haskell/Parsec: LuaList:2006-10/msg00609.html

Lua 5.0 Parser in C++ Spirit

A mostly complete C++ parser of Lua 5.0, which is using Spirit from Boost: http://article.gmane.org/gmane.comp.parsers.spirit.general/4846

This seems like a nice start for reusing in your own things that need a Lua interpreter in C++. The author has abandoned the project, and the above is the latest version as of February 2004. In February 2005, I looked at this grammar closer to try to use it. There are a number of problems with it:

• id's can start with _. Easy to fix.
• Escaped ' and " inside strings are not working. Easy to fix.
• Comments can only appear at statement level. A work-around is to add it to expressions and fields rules, which improves things a lot. Make sure to do *( comment ) instead of just comment to handle comments after each other.
• Long comments --[[ ]] are not supported. Easy to fix by changing comment to shortcomment and longcomment. Make sure to put longcomment first, because spirit is eager.
• a[b] = 2 does not parse. Some function calls are not parsed correctly, i.e. a(b)(). It seems that the refactoring of the left recursion with prefixexp is not done correctly. I have failed to fix this.

The last point is a show-stopper for me. Thus I have failed to make Spirit parse Lua correctly.

-- Asger Ottar Alstrup (aalstrup at laerdal.dk)

Lua 4.1 Grammar

Moved to LuaFourOneGrammar

Lua 4 Interpreter in Java - JLua

An incomplete interpreter of Lua 4 implemented in Java: http://www.hetland.org/jlua/ (broken link)

Lua 2.5 Interpreter in OCaml - Lua-ml

[Lua-ml] is an implementation of Lua 2.5 in OCaml. The parser is constructed with some OCaml parser generator, wrapped up in some literate programming system.