Question

检查以下语法以解析单词SELECT。我正在尝试遵循其词法分析器ATN的逻辑来实现自动完成功能，但这没有任何意义。但是词法分析器正在以某种方式工作...

看词法分析器ATN，似乎两个E片段都使用相同的状态（下面的状态7）实现为一个逻辑实体，尽管它们对如何继续没有相同的约束之后。

这使我的自动完成逻辑混乱了，但是以某种方式却没有使ANTLR4词法分析器接受诸如SELELELECT之类的输入有效。词法化时，我是否错过了一些隐藏在ATN或运行时中某些地方的额外状态？

完整语法：

grammar Expr;
prog: SELECT;
SELECT : S E L E C T;
WS: [ \t\n] -> channel(HIDDEN);
fragment S : [sS];
fragment E : [eE];
fragment L : [lL];
fragment C : [cC];
fragment T : [tT];

生成的词法分析器ATN规则。对于每个规则，我们将打印其开始状态和停止状态。请注意，E以7开头。

 Rule  0 SELECT               start: 1  stop: 2
 Rule  1 WS                   start: 3  stop: 4
 Rule  2 S                    start: 5  stop: 6
 Rule  3 E                    start: 7  stop: 8
 Rule  4 L                    start: 9  stop: 10
 Rule  5 C                    start: 11  stop: 12
 Rule  6 T                    start: 13  stop: 14

这是ATN转换。每行表示从前一行到达的状态到行末打印的状态号的可能转换。请注意带有RuleTransition@4eb7f003-> E RuleStartState 7*的行-星号表示回到状态7会创建循环的事实。

 TokensStartState 0
    epsilon-> SELECT RuleStartState 1
      epsilon-> SELECT BasicState 15
        RuleTransition@ed9d034-> S RuleStartState 5
          epsilon-> S BasicState 26
            {83, 115}-> S BasicState 27
              epsilon-> S RuleStopState 6
                epsilon-> SELECT BasicState 16
                  RuleTransition@6121c9d6-> E RuleStartState 7
                    epsilon-> E BasicState 28
                      {69, 101}-> E BasicState 29
                        epsilon-> E RuleStopState 8
                          epsilon-> SELECT BasicState 17
                            RuleTransition@87f383f-> L RuleStartState 9
                              epsilon-> L BasicState 30
                                {76, 108}-> L BasicState 31
                                  epsilon-> L RuleStopState 10
                                    epsilon-> SELECT BasicState 18
                                      RuleTransition@4eb7f003-> E RuleStartState 7*
                          epsilon-> SELECT BasicState 19
                            RuleTransition@eafc191-> C RuleStartState 11
                              epsilon-> C BasicState 32
                                {67, 99}-> C BasicState 33
                                  epsilon-> C RuleStopState 12
                                    epsilon-> SELECT BasicState 20
                                      RuleTransition@612fc6eb-> T RuleStartState 13
                                        epsilon-> T BasicState 34
                                          {84, 116}-> T BasicState 35
                                            epsilon-> T RuleStopState 14
                                              epsilon-> SELECT BasicState 21
                                                epsilon-> SELECT RuleStopState 2
    epsilon-> WS RuleStartState 3
      epsilon-> WS BasicState 22
        {9..10, 32}-> WS BasicState 23
          epsilon-> WS BasicState 24
            action_1:0-> WS BasicState 25
              epsilon-> WS RuleStopState 4

ANTLR4产生的词法分析器ATN似乎是递归的，但不是

0 个答案: