Question

我看过Bison的帮助并写了这个，但我不确定它是完全正确的。我还需要yylex()来处理词法分析器（它应该是Flex工具）。我知道一些关于无上下文语法的基本知识。但我不知道如何正确实施它们！：（

我想要一个简单的Bison语法用于HTML。问题是：下面的语法应该改变什么？

%{
    #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" '=' FILENAME_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. */
%%

这是Bison的输出：

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

它不会是一个完整的HTML解析器。我只想验证非常简单的HTML文档而没有任何CSS样式或JavaScripts或... 我也看到了this。注意：解决方案必须是Bison语法！

Answer 1

TAG应该是词法分析器返回的一个标记，否则你将编写案例直到奶牛回家。

同样适用于属性等。

需要HTML的简单Bison语法

1 个答案: