Package org.antlr.v4.runtime.atn

Class ATNConfig

java.lang.Object

org.antlr.v4.runtime.atn.ATNConfig

Direct Known Subclasses:

LexerATNConfig

public class ATNConfig
extends Object

A tuple: (ATN state, predicted alt, syntactic, semantic context). The syntactic context is a graph-structured stack node whose path(s) to the root is the rule invocation(s) chain used to arrive at the state. The semantic context is the tree of semantic predicates encountered before reaching an ATN state.

Field Summary

Fields

Modifier and Type	Field	Description
int	alt	What alt (or lexer rule) is predicted by this configuration
PredictionContext	context	The stack of invoking states leading to the rule/states associated with this config.
int	reachesIntoOuterContext	We cannot execute predicates dependent upon local context unless we know for sure we are in the correct context.
SemanticContext	semanticContext
ATNState	state	The ATN state associated with this configuration

Constructor Summary

Constructors

Constructor	Description
ATNConfig(ATNConfig old)
ATNConfig(ATNConfig c, ATNState state)
ATNConfig(ATNConfig c, ATNState state, PredictionContext context)
ATNConfig(ATNConfig c, ATNState state, PredictionContext context, SemanticContext semanticContext)
ATNConfig(ATNConfig c, ATNState state, SemanticContext semanticContext)
ATNConfig(ATNConfig c, SemanticContext semanticContext)
ATNConfig(ATNState state, int alt, PredictionContext context)
ATNConfig(ATNState state, int alt, PredictionContext context, SemanticContext semanticContext)

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object o)	An ATN configuration is equal to another if both have the same state, they predict the same alternative, and syntactic/semantic contexts are the same.
boolean	equals(ATNConfig other)
int	getOuterContextDepth()	This method gets the value of the reachesIntoOuterContext field as it existed prior to the introduction of the isPrecedenceFilterSuppressed() method.
int	hashCode()
boolean	isPrecedenceFilterSuppressed()
void	setPrecedenceFilterSuppressed(boolean value)
String	toString()
String	toString(Recognizer<?,?> recog, boolean showAlt)

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

state

public final ATNState state

The ATN state associated with this configuration

alt

public final int alt

What alt (or lexer rule) is predicted by this configuration

context

public PredictionContext context

The stack of invoking states leading to the rule/states associated with this config. We track only those contexts pushed during execution of the ATN simulator.

reachesIntoOuterContext

public int reachesIntoOuterContext

We cannot execute predicates dependent upon local context unless we know for sure we are in the correct context. Because there is no way to do this efficiently, we simply cannot evaluate dependent predicates unless we are in the rule that initially invokes the ATN simulator.

closure() tracks the depth of how far we dip into the outer context: depth > 0. Note that it may not be totally accurate depth since I don't ever decrement. TODO: make it a boolean then

For memory efficiency, the isPrecedenceFilterSuppressed() method is also backed by this field. Since the field is publicly accessible, the highest bit which would not cause the value to become negative is used to store this field. This choice minimizes the risk that code which only compares this value to 0 would be affected by the new purpose of the flag. It also ensures the performance of the existing ATNConfig constructors as well as certain operations like ATNConfigSet.add(ATNConfig, DoubleKeyMap) method are completely unaffected by the change.

semanticContext

public final SemanticContext semanticContext

Constructor Detail

ATNConfig

public ATNConfig(ATNConfig old)

ATNConfig

public ATNConfig(ATNState state,
                 int alt,
                 PredictionContext context)

ATNConfig

public ATNConfig(ATNState state,
                 int alt,
                 PredictionContext context,
                 SemanticContext semanticContext)

ATNConfig

public ATNConfig(ATNConfig c,
                 ATNState state)

ATNConfig

public ATNConfig(ATNConfig c,
                 ATNState state,
                 SemanticContext semanticContext)

ATNConfig

public ATNConfig(ATNConfig c,
                 SemanticContext semanticContext)

ATNConfig

public ATNConfig(ATNConfig c,
                 ATNState state,
                 PredictionContext context)

ATNConfig

public ATNConfig(ATNConfig c,
                 ATNState state,
                 PredictionContext context,
                 SemanticContext semanticContext)

Method Detail

getOuterContextDepth

public final int getOuterContextDepth()

This method gets the value of the reachesIntoOuterContext field as it existed prior to the introduction of the isPrecedenceFilterSuppressed() method.

isPrecedenceFilterSuppressed

public final boolean isPrecedenceFilterSuppressed()

setPrecedenceFilterSuppressed

public final void setPrecedenceFilterSuppressed(boolean value)

equals

public boolean equals(Object o)

An ATN configuration is equal to another if both have the same state, they predict the same alternative, and syntactic/semantic contexts are the same.

Overrides:

equals in class Object

equals

public boolean equals(ATNConfig other)

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

toString

public String toString(Recognizer<?,?> recog,
                       boolean showAlt)