I've looked at the Bison help and have written this, but I'm not sure it's completely correct. Also i need an yylex()
that handle Lexical Analyzer (It should be Flex
tool). I know some basic things about context-free grammars. But i don't know how to implement them correctly! :(
I want a simple Bison grammar for HTML. The question is: What should change in following grammar?
%{
#include <stdio.h>
int yylex(void);
int yyerror(char const *);
%}
%token NUM_TOKEN FILENAME_TOKEN COLOR_TOKEN NAME_TOKEN
/* Html Grammer follows... */
%%
/* Any html tag follow this pattern: */
EXPRESSION:
'<' TAG CLUSER '>' INNER_EXPRESSION "</" TAG '>' ;
/* Some html tags: */
TAG:
"a" |
"html" |
"head" |
"link" |
"div" |
"input"|
"from" |
"title"|
"img" |
"table"|
"td" |
"tr" ;
CLUSER:
ALIGN|
CLASS|
ID|
SRC|
TEPY|
ACTION|
HREF|
REL|
/* € (Eplsilone) */
;
ALIGN:
"align" '=' "left"|
"align" '=' "right"|
"align" '=' "center"
;
CLASS:
"class" '=' NAME_TOKEN
;
ID:
"id" '=' NAME_TOKEN
;
SRC:
"src" '=' FILE开发者_StackOverflow社区NAME_TOKEN
;
TEPY:
"type" '=' CONT
;
ACTION:
"action" '=' FILENAME_TOKEN
;
HREF:
"href" '=' '\"#\"'|
"href" '=' FILENAME_TOKEN
;
REL:
"rel" '=' "stylesheet"|
"rel" '=' "\"stylesheet\""
;
DOMIN:
"px"|
"mm"|
"cm"|
"inch"
;
PAS:
"php"|
"asp"|
"aspx"|
"css"
;
CONT:
"button"|
"checkbox"|
"text"|
"password"|
"file"|
"submit"
;
INNER_EXPRESSION:
EXPRESSION|
/* € (Eplsilone) */
;
/* Html grammer ends. */
%%
This is Bison's output:
E:\Program Files\GnuWin32\bin>bison "E:\Dev-Cpp\HtmlBison\html.y" -o "E:\html.c"
E:\Dev-Cpp\HtmlBison\html.y: warning: 2 nonterminals useless in grammar
E:\Dev-Cpp\HtmlBison\html.y: warning: 8 rules useless in grammar
E:\\Dev-Cpp\\HtmlBison\\html.y:83.1-5: warning: nonterminal useless in grammar:
DOMIN
E:\\Dev-Cpp\\HtmlBison\\html.y:90.1-3: warning: nonterminal useless in grammar:
PAS
E:\\Dev-Cpp\\HtmlBison\\html.y:84.7-10: warning: rule useless in grammar: DOMIN:
"px"
E:\\Dev-Cpp\\HtmlBison\\html.y:85.7-10: warning: rule useless in grammar: DOMIN:
"mm"
E:\\Dev-Cpp\\HtmlBison\\html.y:86.7-10: warning: rule useless in grammar: DOMIN:
"cm"
E:\\Dev-Cpp\\HtmlBison\\html.y:87.7-12: warning: rule useless in grammar: DOMIN:
"inch"
E:\\Dev-Cpp\\HtmlBison\\html.y:91.6-10: warning: rule useless in grammar: PAS: "
php"
E:\\Dev-Cpp\\HtmlBison\\html.y:92.6-10: warning: rule useless in grammar: PAS: "
asp"
E:\\Dev-Cpp\\HtmlBison\\html.y:93.6-11: warning: rule useless in grammar: PAS: "
aspx"
E:\\Dev-Cpp\\HtmlBison\\html.y:94.6-10: warning: rule useless in grammar: PAS: "
css"
m4: cannot open `Files\GnuWin32/share/bison': No such file or directory
m4: cannot open `E:\Program': No such file or directory
m4: cannot open `Files\GnuWin32/share/bison/m4sugar/m4sugar.m4': No such file or
directory
It's not going to be a complete HTML parser. I just want to validate very simple HTML documents without any CSS
styles or JavaScripts
or ...
I also saw this.
NOTE: The Solution must be a Bison grammar!
TAG
should be a token that is returned from a lexer, else you will be writing cases till the cows come home.
Same goes for attributes, etc.
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