org.antlr.v4.runtime.atn

Class ATN

java.lang.Object

org.antlr.v4.runtime.atn.ATN

public class ATN
extends Object

Field Summary

Fields

Modifier and Type	Field and Description
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.
ATNType	grammarType The type of the ATN.
static int	INVALID_ALT_NUMBER
LexerAction[]	lexerActions For lexer ATNs, this is an array of LexerAction objects which may be referenced by action transitions in the ATN.
int	maxTokenType The maximum value for any symbol recognized by a transition in the ATN.
Map<String,TokensStartState>	modeNameToStartState
List<TokensStartState>	modeToStartState
RuleStartState[]	ruleToStartState Maps from rule index to starting state number.
RuleStopState[]	ruleToStopState Maps from rule index to stop state number.
int[]	ruleToTokenType For lexer ATNs, this maps the rule index to the resulting token type.
List<ATNState>	states

Constructor Summary

Constructors

Constructor and Description
ATN(ATNType grammarType, int maxTokenType) Used for runtime deserialization of ATNs from strings

Method Summary

Modifier and Type	Method and Description
void	addState(ATNState state)
int	defineDecisionState(DecisionState s)
DecisionState	getDecisionState(int decision)
IntervalSet	getExpectedTokens(int stateNumber, RuleContext context) Computes the set of input symbols which could follow ATN state number stateNumber in the specified full context.
int	getNumberOfDecisions()
IntervalSet	nextTokens(ATNState s) Compute the set of valid tokens that can occur starting in s and staying in same rule.
IntervalSet	nextTokens(ATNState s, RuleContext ctx) Compute the set of valid tokens that can occur starting in state s.
void	removeState(ATNState state)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INVALID_ALT_NUMBER

public static final int INVALID_ALT_NUMBER

See Also:

Constant Field Values

states

public final List<ATNState> states

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.

modeNameToStartState

public final Map<String,TokensStartState> modeNameToStartState

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.

modeToStartState

public final List<TokensStartState> modeToStartState

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 RuleContext.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 https://github.com/antlr/antlr4/issues/1428 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.

Parameters:

stateNumber - the ATN state number

context - the full parse context

Returns:

The set of potentially valid input symbols which could follow the specified state in the specified context.

Throws:

IllegalArgumentException - if the ATN does not contain a state with number stateNumber