any version of CSS) grammar
(Это приложение является формальным)
The minimal CSS (i.e., any version of CSS) grammar that all implementations need to support is defined in section 7. The grammar below defines a much smaller language, a language that defines the syntax of CSS1.
It is in some sense, however, still a superset of CSS1: there are additional semantic constraints not expressed in this grammar. A conforming UA must also adhere to the forward-compatible parsing rules (section 7.1), the property and value notation (section 5) and the unit notation (section 6). In addition, HTML imposes restrictions, e.g., on the possible values of the CLASS attribute.
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 CSS1 syntax). The format of the productions is optimized for human consumption and some shorthand notation beyond yacc [15] is used: * : 0 or more + : 1 or more ? : 0 or 1 | : separates alternatives [] : grouping
The productions are:
stylesheet : [CDO|CDC]* [ import [CDO|CDC]* ]* [ ruleset [CDO|CDC]* ]* ; import : IMPORT_SYM [STRING|URL] ';' /* E.g., @import url(fun.css); */ ; 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;} "!"{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);}
