grammar.txt

selectors_group
  : selector [ COMMA S* selector ]*
  ;

selector
  : simple_selector_sequence [ combinator simple_selector_sequence ]*
  ;

combinator
  /* combinators can be surrounded by whitespace */
  : PLUS S* | GREATER S* | TILDE S* | S+
  ;

simple_selector_sequence
  : [ type_selector | universal ]
    [ HASH | class | attrib | pseudo | negation ]*
  | [ HASH | class | attrib | pseudo | negation ]+
  ;

type_selector
  : [ namespace_prefix ]? element_name
  ;

/* not supported */
namespace_prefix
  : [ IDENT | '*' ]? '|'
  ;

element_name
  : IDENT
  ;

universal
  : [ namespace_prefix ]? '*'
  ;

class
  : '.' IDENT
  ;

attrib
  : '[' S* [ namespace_prefix ]? IDENT S*
        [ [ PREFIXMATCH |
            SUFFIXMATCH |
            SUBSTRINGMATCH |
            '=' |
            INCLUDES |
            DASHMATCH ] S* [ IDENT | STRING ] S*
        ]? ']'
  ;

pseudo
  /* '::' starts a pseudo-element, ':' a pseudo-class */
  /* Exceptions: :first-line, :first-letter, :before and :after. */
  /* Note that pseudo-elements are restricted to one per selector and */
  /* occur only in the last simple_selector_sequence. */
  : ':' ':'? [ IDENT | functional_pseudo ]
  ;

functional_pseudo
  : FUNCTION S* expression ')'
  ;

expression
  /* In CSS3, the expressions are identifiers, strings, */
  /* or of the form "an+b" */
  : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
  ;

negation
  : NOT S* negation_arg S* ')'
  ;

negation_arg
  : type_selector | universal | HASH | class | attrib | pseudo
  ;

%option case-insensitive

ident     [-]?{nmstart}{nmchar}*
name      {nmchar}+
nmstart   [_a-z]|{nonascii}|{escape}
nonascii  [^\0-\177]
unicode   \\[0-9a-f]{1,6}(\r\n|[ \n\r\t\f])?
escape    {unicode}|\\[^\n\r\f0-9a-f]
nmchar    [_a-z0-9-]|{nonascii}|{escape}
num       [0-9]+|[0-9]*\.[0-9]+
string    {string1}|{string2}
string1   \"([^\n\r\f\\"]|\\{nl}|{nonascii}|{escape})*\"
string2   \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
invalid   {invalid1}|{invalid2}
invalid1  \"([^\n\r\f\\"]|\\{nl}|{nonascii}|{escape})*
invalid2  \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
nl        \n|\r\n|\r|\f
w         [ \t\r\n\f]*

D         d|\\0{0,4}(44|64)(\r\n|[ \t\r\n\f])?
E         e|\\0{0,4}(45|65)(\r\n|[ \t\r\n\f])?
N         n|\\0{0,4}(4e|6e)(\r\n|[ \t\r\n\f])?|\\n
O         o|\\0{0,4}(4f|6f)(\r\n|[ \t\r\n\f])?|\\o
T         t|\\0{0,4}(54|74)(\r\n|[ \t\r\n\f])?|\\t
V         v|\\0{0,4}(58|78)(\r\n|[ \t\r\n\f])?|\\v

%%

[ \t\r\n\f]+     return S;

"~="             return INCLUDES;
"|="             return DASHMATCH;
"^="             return PREFIXMATCH;
"$="             return SUFFIXMATCH;
"*="             return SUBSTRINGMATCH;
{ident}          return IDENT;
{string}         return STRING;
{ident}"("       return FUNCTION;
{num}            return NUMBER;
"#"{name}        return HASH;
{w}"+"           return PLUS;
{w}">"           return GREATER;
{w}","           return COMMA;
{w}"~"           return TILDE;
":"{N}{O}{T}"("  return NOT;
@{ident}         return ATKEYWORD;
{invalid}        return INVALID;
{num}%           return PERCENTAGE;
{num}{ident}     return DIMENSION;
"<!--"           return CDO;
"-->"            return CDC;

\/\*[^*]*\*+([^/*][^*]*\*+)*\/                    /* ignore comments */

.                return *yytext;