org.antlr.v4.runtime.atn

Class LL1Analyzer

java.lang.Object

org.antlr.v4.runtime.atn.LL1Analyzer

public class LL1Analyzer
extends Object

Field Summary

Fields

Modifier and Type	Field and Description
ATN	atn
static int	HIT_PRED Special value added to the lookahead sets to indicate that we hit a predicate during analysis if seeThruPreds==false.

Constructor Summary

Constructors

Constructor and Description
LL1Analyzer(ATN atn)

Method Summary

Methods

Modifier and Type	Method and Description
protected void	_LOOK(ATNState s, PredictionContext ctx, IntervalSet look, Set<ATNConfig> lookBusy, boolean seeThruPreds, boolean addEOF) Compute set of tokens that can come next.
IntervalSet[]	getDecisionLookahead(ATNState s) From an ATN state, s, find the set of all labels reachable from s at depth k.
IntervalSet	LOOK(ATNState s, RuleContext ctx) Get lookahead, using ctx if we reach end of rule.

Methods inherited from class java.lang.Object

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

Field Detail

HIT_PRED

public static final int HIT_PRED

Special value added to the lookahead sets to indicate that we hit a predicate during analysis if seeThruPreds==false.

See Also:

Constant Field Values

atn

@NotNull
public final ATN atn

Constructor Detail

LL1Analyzer

public LL1Analyzer(@NotNull
           ATN atn)

Method Detail

getDecisionLookahead

@Nullable
public IntervalSet[] getDecisionLookahead(@Nullable
                                          ATNState s)

From an ATN state, s, find the set of all labels reachable from s at depth k. Only for DecisionStates.

LOOK

@NotNull
public IntervalSet LOOK(@NotNull
                       ATNState s,
                       @Nullable
                       RuleContext ctx)

Get lookahead, using ctx if we reach end of rule. If ctx is null or EMPTY, don't chase FOLLOW. If ctx is null, EPSILON is in set if we can reach end of rule. If ctx is EMPTY, EOF is in set if we can reach end of rule.

_LOOK

protected void _LOOK(@NotNull
         ATNState s,
         @Nullable
         PredictionContext ctx,
         @NotNull
         IntervalSet look,
         @NotNull
         Set<ATNConfig> lookBusy,
         boolean seeThruPreds,
         boolean addEOF)

Compute set of tokens that can come next. If the context is EMPTY, then we don't go anywhere when we hit the end of the rule. We have the correct set. If the context is null, that means that we did not want any tokens following this rule--just the tokens that could be found within this rule. Add EPSILON to the set indicating we reached the end of the ruled out having to match a token.