Package org.antlr.v4.runtime.atn
Class ATN
- java.lang.Object
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- org.antlr.v4.runtime.atn.ATN
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public class ATN extends Object
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Field Summary
Fields Modifier and Type Field 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 ofLexerAction
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
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method 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 numberstateNumber
in the specified fullcontext
.int
getNumberOfDecisions()
IntervalSet
nextTokens(ATNState s)
Compute the set of valid tokens that can occur starting ins
and staying in same rule.IntervalSet
nextTokens(ATNState s, RuleContext ctx)
Compute the set of valid tokens that can occur starting in states
.void
removeState(ATNState state)
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Field Detail
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INVALID_ALT_NUMBER
public static final int INVALID_ALT_NUMBER
- See Also:
- Constant Field Values
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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...
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ruleToStartState
public RuleStartState[] ruleToStartState
Maps from rule index to starting state number.
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ruleToStopState
public RuleStopState[] ruleToStopState
Maps from rule index to stop state number.
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modeNameToStartState
public final Map<String,TokensStartState> modeNameToStartState
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grammarType
public final ATNType grammarType
The type of the ATN.
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maxTokenType
public final int maxTokenType
The maximum value for any symbol recognized by a transition in the ATN.
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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 theATNDeserializationOptions.isGenerateRuleBypassTransitions()
deserialization option was specified; otherwise, this isnull
.
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lexerActions
public LexerAction[] lexerActions
For lexer ATNs, this is an array ofLexerAction
objects which may be referenced by action transitions in the ATN.
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modeToStartState
public final List<TokensStartState> modeToStartState
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Constructor Detail
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ATN
public ATN(ATNType grammarType, int maxTokenType)
Used for runtime deserialization of ATNs from strings
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Method Detail
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nextTokens
public IntervalSet nextTokens(ATNState s, RuleContext ctx)
Compute the set of valid tokens that can occur starting in states
. Ifctx
is null, the set of tokens will not include what can follow the rule surroundings
. In other words, the set will be restricted to tokens reachable staying withins
's rule.
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nextTokens
public IntervalSet nextTokens(ATNState s)
Compute the set of valid tokens that can occur starting ins
and staying in same rule.Token.EPSILON
is in set if we reach end of rule.
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addState
public void addState(ATNState state)
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removeState
public void removeState(ATNState state)
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defineDecisionState
public int defineDecisionState(DecisionState s)
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getDecisionState
public DecisionState getDecisionState(int decision)
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getNumberOfDecisions
public int getNumberOfDecisions()
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getExpectedTokens
public IntervalSet getExpectedTokens(int stateNumber, RuleContext context)
Computes the set of input symbols which could follow ATN state numberstateNumber
in the specified fullcontext
. 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 theRuleStopState
of the outermost context without matching any symbols,Token.EOF
is added to the returned set.If
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.context
isnull
, it is treated asRuleContext.EMPTY
.- Parameters:
stateNumber
- the ATN state numbercontext
- 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 numberstateNumber
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