Question

我有以下yacc语法：

OPTIONS:OPTIONS OPTION                  {printf("%s\n", "Options    enabled");}
        | OPTION                        {printf("%s\n",     "First option");}
        |
        ;

OPTION:   DEBUG                         {printf("%s\n",   "debug enabled");}
        | NESTING                       {printf("%s\n", "nesting enabled");}
        | '(' STACK '=' NAME ')'        {printf("%s\n", "stack size given");}
    | NOLIST                        {printf("%s\n", "nolist enabled");}
    | VIEW EQ NAME                  {printf("%s\n", "this is a view, first name is view name");}
    ;

对于空规则，它给我转移/减少错误。该错误的Y.output文件如下所示：

17 OPTIONS: . OPTIONS OPTION
18        | . OPTION
19        | .  [SEMICOLON, VIEW, DEBUG, NESTING, NOLIST, '(']
20 OPTION: . DEBUG
21       | . NESTING
22       | . '(' STACK '=' NAME ')'
23       | . NOLIST
24       | . VIEW EQ NAME

NAME     shift, and go to state 4
VIEW     shift, and go to state 11
DEBUG    shift, and go to state 12
NESTING  shift, and go to state 13
NOLIST   shift, and go to state 14
'('      shift, and go to state 15

VIEW      [reduce using rule 19 (OPTIONS)]
DEBUG     [reduce using rule 19 (OPTIONS)]
NESTING   [reduce using rule 19 (OPTIONS)]
NOLIST    [reduce using rule 19 (OPTIONS)]
'('       [reduce using rule 19 (OPTIONS)]
$default  reduce using rule 19 (OPTIONS)

有人可以建议，如何解决这个问题？

Answer 1

您对规则OPTIONS有一个递归。 conflit存在是因为有两种方法可以阻止递归。例如，看看，如果您只有一个选项，则有两种不同的解析树。

OPTIONS         or                OPTIONS
   |                               |    \
 OPTION                        OPTIONS  OPTION
   |                               |
  ...                       "empty rule"

因此，删除空规则或OPTIONS : OPTION（维护空规则），问题应该消失。

在野牛中使用空规则减少错误

1 个答案: