Class ATN

  • public class ATN
    extends Object
    • Field Detail

      • decisionToState

        public final List<DecisionState> decisionToState
        Each subrule/rule is a decision point and we must track them so we can go back later and build DFA predictors for them. This includes all the rules, subrules, optional blocks, ()+, ()* etc...
      • ruleToStartState

        public RuleStartState[] ruleToStartState
        Maps from rule index to starting state number.
      • ruleToStopState

        public RuleStopState[] ruleToStopState
        Maps from rule index to stop state number.
      • grammarType

        public final ATNType grammarType
        The type of the ATN.
      • maxTokenType

        public final int maxTokenType
        The maximum value for any symbol recognized by a transition in the ATN.
      • ruleToTokenType

        public int[] ruleToTokenType
        For lexer ATNs, this maps the rule index to the resulting token type. For parser ATNs, this maps the rule index to the generated bypass token type if the ATNDeserializationOptions.isGenerateRuleBypassTransitions() deserialization option was specified; otherwise, this is null.
      • lexerActions

        public LexerAction[] lexerActions
        For lexer ATNs, this is an array of LexerAction objects which may be referenced by action transitions in the ATN.
    • Constructor Detail

      • ATN

        public ATN​(ATNType grammarType,
                   int maxTokenType)
        Used for runtime deserialization of ATNs from strings
    • Method Detail

      • nextTokens

        public IntervalSet nextTokens​(ATNState s,
                                      RuleContext ctx)
        Compute the set of valid tokens that can occur starting in state s. If ctx is null, the set of tokens will not include what can follow the rule surrounding s. In other words, the set will be restricted to tokens reachable staying within s's rule.
      • nextTokens

        public IntervalSet nextTokens​(ATNState s)
        Compute the set of valid tokens that can occur starting in s and staying in same rule. Token.EPSILON is in set if we reach end of rule.
      • addState

        public void addState​(ATNState state)
      • removeState

        public void removeState​(ATNState state)
      • defineDecisionState

        public int defineDecisionState​(DecisionState s)
      • getDecisionState

        public DecisionState getDecisionState​(int decision)
      • getNumberOfDecisions

        public int getNumberOfDecisions()
      • getExpectedTokens

        public IntervalSet getExpectedTokens​(int stateNumber,
                                             RuleContext context)
        Computes the set of input symbols which could follow ATN state number stateNumber in the specified full context. This method considers the complete parser context, but does not evaluate semantic predicates (i.e. all predicates encountered during the calculation are assumed true). If a path in the ATN exists from the starting state to the RuleStopState of the outermost context without matching any symbols, Token.EOF is added to the returned set.

        If context is null, it is treated as ParserRuleContext.EMPTY.

        Note that this does NOT give you the set of all tokens that could appear at a given token position in the input phrase. In other words, it does not answer: "Given a specific partial input phrase, return the set of all tokens that can follow the last token in the input phrase." The big difference is that with just the input, the parser could land right in the middle of a lookahead decision. Getting all *possible* tokens given a partial input stream is a separate computation. See For this function, we are specifying an ATN state and call stack to compute what token(s) can come next and specifically: outside of a lookahead decision. That is what you want for error reporting and recovery upon parse error.
        stateNumber - the ATN state number
        context - the full parse context
        The set of potentially valid input symbols which could follow the specified state in the specified context.
        IllegalArgumentException - if the ATN does not contain a state with number stateNumber