Package 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	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	Description
LL1Analyzer(ATN atn)

Method Summary

Modifier and Type	Method	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, RuleContext ctx)	Compute set of tokens that can follow s in the ATN in the specified ctx.
IntervalSet	LOOK(ATNState s, RuleContext 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

public final ATN atn

Constructor Detail

LL1Analyzer

public LL1Analyzer(ATN atn)

Method Detail

getDecisionLookahead

public IntervalSet[] getDecisionLookahead(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

public IntervalSet LOOK(ATNState s,
                        RuleContext 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

public IntervalSet LOOK(ATNState s,
                        ATNState stopState,
                        RuleContext 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

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(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.

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