CSS grammar according to mobileOK Basic 1.0


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

The productions are:

stylesheet
 : [S|CDO|CDC]* [ import [S|CDO|CDC]* ]* [ [ ruleset | media ] [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*
  ;
unary_operator
 : '-' | '+'
 ;
operator
 : '/' | ',' | /* empty */
 ;
property
 : IDENT
 ;
ruleset
 : selector [ ',' selector ]*
   '{' declaration [ ';' declaration ]* '}'
 ;
selector
 : simple_selector+ [ pseudo_element | solitary_pseudo_element ]?
 | solitary_pseudo_element
 ;
  /* An "id" is an ID that is attached to an element type
  ** on its left, as in: P#p007
  ** A "solitary_id" is an ID that is not so attached,
  ** as in: #p007
  ** Analogously for classes and pseudo-classes.
  */
simple_selector
 : element_name id? class? pseudo_class?  /* eg: H1.subject */
 | solitary_id class? pseudo_class?   /* eg: #xyz33 */
 | solitary_class pseudo_class?     /* eg: .author */
 | solitary_pseudo_class      /* eg: :link */
 ;
element_name
 : IDENT
 ;
pseudo_class          /* as in:  A:link */
 : LINK_PSCLASS_AFTER_IDENT
 | VISITED_PSCLASS_AFTER_IDENT
 | ACTIVE_PSCLASS_AFTER_IDENT
 ;
solitary_pseudo_class       /* as in:  :link */
 : LINK_PSCLASS
 | VISITED_PSCLASS
 | ACTIVE_PSCLASS
 ;
class           /* as in:  P.note */
 : CLASS_AFTER_IDENT
 ;
solitary_class          /* as in:  .note */
 : CLASS
 ;
pseudo_element          /* as in:  P:first-line */
 : FIRST_LETTER_AFTER_IDENT
 | FIRST_LINE_AFTER_IDENT
 ;
solitary_pseudo_element       /* as in:  :first-line */
 : FIRST_LETTER
 | FIRST_LINE
 ;
  /* There is a constraint on the id and solitary_id that the
  ** part after the "#" must be a valid HTML ID value;
  ** e.g., "#x77" is OK, but "#77" is not.
  */
id
 : HASH_AFTER_IDENT
 ;
solitary_id
 : HASH
 ;
declaration
 : property ':' expr prio?
 | /* empty */        /* Prevents syntax errors... */
 ;
prio
 : IMPORTANT_SYM      /* !important */
 ;
expr
 : term [ operator term ]*
 ;
term
 : unary_operator?
   [ NUMBER | STRING | PERCENTAGE | LENGTH | EMS | EXS
   | IDENT | hexcolor | URL | RGB ]
 ;
  /* 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 | HASH_AFTER_IDENT
 ;

The following is the tokenizer, written in flex [16] notation. Note that this assumes an 8-bit implementation of flex. The tokenizer is case-insensitive (flex command line option -i).

unicode        \\[0-9a-f]{1,4}
latin1         [¡-ÿ]
escape         {unicode}|\\[ -~¡-ÿ]
stringchar     {escape}|{latin1}|[ !#$%&(-~]
nmstrt         [a-z]|{latin1}|{escape}
nmchar         [-a-z0-9]|{latin1}|{escape}
ident          {nmstrt}{nmchar}*
name           {nmchar}+
d              [0-9]
notnm          [^-a-z0-9\\]|{latin1}
w              [ \t\n]*
num            {d}+|{d}*\.{d}+
string         \"({stringchar}|\')*\"|\'({stringchar}|\")*\'

%x COMMENT
%s AFTER_IDENT

%%
"/*"                           {BEGIN(COMMENT);}
<COMMENT>"*/"                  {BEGIN(0);}
<COMMENT>\n                    {/* ignore */}
<COMMENT>.                     {/* ignore */}
@import                        {BEGIN(0); return IMPORT_SYM;}
@media                         {BEGIN(0); return MEDIA_SYM;}
"!"{w}important                {BEGIN(0); return IMPORTANT_SYM;}
{ident}                        {BEGIN(AFTER_IDENT); return IDENT;}
{string}                       {BEGIN(0); return STRING;}

{num}                          {BEGIN(0); return NUMBER;}
{num}"%"                       {BEGIN(0); return PERCENTAGE;}
{num}pt/{notnm}                {BEGIN(0); return LENGTH;}
{num}mm/{notnm}                {BEGIN(0); return LENGTH;}
{num}cm/{notnm}                {BEGIN(0); return LENGTH;}
{num}pc/{notnm}                {BEGIN(0); return LENGTH;}
{num}in/{notnm}                {BEGIN(0); return LENGTH;}
{num}px/{notnm}                {BEGIN(0); return LENGTH;}
{num}em/{notnm}                {BEGIN(0); return EMS;}
{num}ex/{notnm}                {BEGIN(0); return EXS;}

<AFTER_IDENT>":"link           {return LINK_PSCLASS_AFTER_IDENT;}
<AFTER_IDENT>":"visited        {return VISITED_PSCLASS_AFTER_IDENT;}
<AFTER_IDENT>":"active         {return ACTIVE_PSCLASS_AFTER_IDENT;}
<AFTER_IDENT>":"first-line     {return FIRST_LINE_AFTER_IDENT;}
<AFTER_IDENT>":"first-letter   {return FIRST_LETTER_AFTER_IDENT;}
<AFTER_IDENT>"#"{name}         {return HASH_AFTER_IDENT;}
<AFTER_IDENT>"."{name}         {return CLASS_AFTER_IDENT;}

":"link                        {BEGIN(AFTER_IDENT); return LINK_PSCLASS;}
":"visited                     {BEGIN(AFTER_IDENT); return VISITED_PSCLASS;}
":"active                      {BEGIN(AFTER_IDENT); return ACTIVE_PSCLASS;}
":"first-line                  {BEGIN(AFTER_IDENT); return FIRST_LINE;}
":"first-letter                {BEGIN(AFTER_IDENT); return FIRST_LETTER;}
"#"{name}                      {BEGIN(AFTER_IDENT); return HASH;}
"."{name}                      {BEGIN(AFTER_IDENT); return CLASS;}

url\({w}{string}{w}\)                                  |
url\({w}([^ \n\'\")]|\\\ |\\\'|\\\"|\\\))+{w}\)        {BEGIN(0); return URL;}
rgb\({w}{num}%?{w}\,{w}{num}%?{w}\,{w}{num}%?{w}\)     {BEGIN(0); return RGB;}

[-/+{};,#:]                    {BEGIN(0); return *yytext;}
[ \t]+                         {BEGIN(0); /* ignore whitespace */}
\n                             {BEGIN(0); /* ignore whitespace */}
\<\!\-\-                       {BEGIN(0); return CDO;}
\-\-\>                         {BEGIN(0); return CDC;}
.                              {fprintf(stderr, "%d: Illegal character (%d)\n",
                                lineno, *yytext);}