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, ATNState stopState, PredictionContext ctx, IntervalSet look, Set<ATNConfig> lookBusy, BitSet calledRuleStack, boolean seeThruPreds, boolean addEOF) Compute set of tokens that can follow s in the ATN in the specified ctx.
IntervalSet[]	getDecisionLookahead(ATNState s) Calculates the SLL(1) expected lookahead set for each outgoing transition of an ATNState.
IntervalSet	LOOK(ATNState s, ATNState stopState, PredictionContext ctx) Compute set of tokens that can follow s in the ATN in the specified ctx.
IntervalSet	LOOK(ATNState s, PredictionContext ctx) Compute set of tokens that can follow s in the ATN in the specified ctx.

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)

Calculates the SLL(1) expected lookahead set for each outgoing transition of an ATNState. The returned array has one element for each outgoing transition in s. If the closure from transition i leads to a semantic predicate before matching a symbol, the element at index i of the result will be null.

Parameters:

s - the ATN state

Returns:

the expected symbols for each outgoing transition of s.

LOOK

@NotNull
public IntervalSet LOOK(@NotNull
                       ATNState s,
                       @NotNull
                       PredictionContext ctx)

Compute set of tokens that can follow s in the ATN in the specified ctx.

If ctx is null and the end of the rule containing s is reached, Token.EPSILON is added to the result set. If ctx is not null and the end of the outermost rule is reached, Token.EOF is added to the result set.

Parameters:

s - the ATN state

ctx - the complete parser context, or null if the context should be ignored

Returns:

The set of tokens that can follow s in the ATN in the specified ctx.

LOOK

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

Compute set of tokens that can follow s in the ATN in the specified ctx.

If ctx is null and the end of the rule containing s is reached, Token.EPSILON is added to the result set. If ctx is not PredictionContext#EMPTY_LOCAL and the end of the outermost rule is reached, Token.EOF is added to the result set.

Parameters:

s - the ATN state

stopState - the ATN state to stop at. This can be a BlockEndState to detect epsilon paths through a closure.

ctx - the complete parser context, or null if the context should be ignored

Returns:

The set of tokens that can follow s in the ATN in the specified ctx.

_LOOK

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

Compute set of tokens that can follow s in the ATN in the specified ctx.

If ctx is PredictionContext.EMPTY_LOCAL and stopState or the end of the rule containing s is reached, Token.EPSILON is added to the result set. If ctx is not PredictionContext.EMPTY_LOCAL and addEOF is true and stopState or the end of the outermost rule is reached, Token.EOF is added to the result set.

Parameters:

s - the ATN state.

stopState - the ATN state to stop at. This can be a BlockEndState to detect epsilon paths through a closure.

ctx - The outer context, or PredictionContext.EMPTY_LOCAL if the outer context should not be used.

look - The result lookahead set.

lookBusy - A set used for preventing epsilon closures in the ATN from causing a stack overflow. Outside code should pass new HashSet<ATNConfig> for this argument.

calledRuleStack - A set used for preventing left recursion in the ATN from causing a stack overflow. Outside code should pass new BitSet() for this argument.

seeThruPreds - true to true semantic predicates as implicitly true and "see through them", otherwise false to treat semantic predicates as opaque and add HIT_PRED to the result if one is encountered.

addEOF - Add Token.EOF to the result if the end of the outermost context is reached. This parameter has no effect if ctx is PredictionContext.EMPTY_LOCAL.