CSS3 Grammar

The grammar below is LL(1) (but note that most UA's should not use it directly, since it doesn't express the parsing conventions, only the CSS2 syntax). The format of the productions is optimized for human consumption and some shorthand notation beyond Yacc (see [YACC]) is used:

• *: 0 or more
• +: 1 or more
• ?: 0 or 1
• |: separates alternatives
• [ ]: grouping

The productions are:

stylesheet
 : [ CHARSET_SYM S* STRING S* ';' ]?
   [S|CDO|CDC]* [ import [S|CDO|CDC]* ]*
   [ [ ruleset | media | page | font_face ] [S|CDO|CDC]* ]*
 ;
import
 : IMPORT_SYM S*
   [STRING|URI] S* [ medium [ ',' S* medium]* ]? ';' S*
 ;
media
 : MEDIA_SYM S* medium [ ',' S* medium ]* '{' S* ruleset* '}' S*
 ;
medium
 : IDENT S*
 ;
page
 : PAGE_SYM S* IDENT? pseudo_page? S*
   '{' S* declaration [ ';' S* declaration ]* '}' S*
 ;
pseudo_page
 : ':' IDENT
 ;
font_face
 : FONT_FACE_SYM S*
   '{' S* declaration [ ';' S* declaration ]* '}' S*
 ;
operator
 : '/' S* | ',' S* | /* empty */
 ;
combinator
 : '+' S* | '>' S* | /* empty */
 ;
unary_operator
 : '-' | '+'
 ;
property
 : IDENT S*
 ;
ruleset
 : selector [ ',' S* selector ]*
   '{' S* declaration [ ';' S* declaration ]* '}' S*
 ;
selector
 : simple_selector [ combinator simple_selector ]*
 ;
simple_selector
 : element_name? [ HASH | class | attrib | pseudo ]* S*
 ;
class
 : '.' IDENT
 ;
element_name
 : IDENT | '*'
 ;
attrib
 : '[' S* IDENT S* [ [ '=' | INCLUDES | DASHMATCH ] S*
   [ IDENT | STRING ] S* ]? ']'
 ;
pseudo
 : ':' [ IDENT | FUNCTION S* IDENT S* ')' ]
 ;
declaration
 : property ':' S* expr prio?
 | /* empty */
 ;
prio
 : IMPORTANT_SYM S*
 ;
expr
 : term [ operator term ]*
 ;
term
 : unary_operator?
   [ NUMBER S* | PERCENTAGE S* | LENGTH S* | EMS S* | EXS S* | ANGLE S* |
     TIME S* | FREQ S* | function ]
 | STRING S* | IDENT S* | URI S* | RGB S* | UNICODERANGE S* | hexcolor
 ;
function
 : FUNCTION S* expr ')' S*
 ;
/*
* There is a constraint on the color that it must
* have either 3 or 6 hex-digits (i.e., [0-9a-fA-F])
* after the "#"; e.g., "#000" is OK, but "#abcd" is not.
*/
hexcolor
 : HASH S*
 ;