org.antlr.v4.runtime.atn.AmbiguityInfo Maven / Gradle / Ivy
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/*
* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
package org.antlr.v4.runtime.atn;
import org.antlr.v4.runtime.ANTLRErrorListener;
import org.antlr.v4.runtime.TokenStream;
import java.util.BitSet;
/**
* This class represents profiling event information for an ambiguity.
* Ambiguities are decisions where a particular input resulted in an SLL
* conflict, followed by LL prediction also reaching a conflict state
* (indicating a true ambiguity in the grammar).
*
*
* This event may be reported during SLL prediction in cases where the
* conflicting SLL configuration set provides sufficient information to
* determine that the SLL conflict is truly an ambiguity. For example, if none
* of the ATN configurations in the conflicting SLL configuration set have
* traversed a global follow transition (i.e.
* {@link ATNConfig#reachesIntoOuterContext} is 0 for all configurations), then
* the result of SLL prediction for that input is known to be equivalent to the
* result of LL prediction for that input.
*
*
* In some cases, the minimum represented alternative in the conflicting LL
* configuration set is not equal to the minimum represented alternative in the
* conflicting SLL configuration set. Grammars and inputs which result in this
* scenario are unable to use {@link PredictionMode#SLL}, which in turn means
* they cannot use the two-stage parsing strategy to improve parsing performance
* for that input.
*
* @see ParserATNSimulator#reportAmbiguity
* @see ANTLRErrorListener#reportAmbiguity
*
* @since 4.3
*/
public class AmbiguityInfo extends DecisionEventInfo {
/** The set of alternative numbers for this decision event that lead to a valid parse. */
public BitSet ambigAlts;
/**
* Constructs a new instance of the {@link AmbiguityInfo} class with the
* specified detailed ambiguity information.
*
* @param decision The decision number
* @param configs The final configuration set identifying the ambiguous
* alternatives for the current input
* @param ambigAlts The set of alternatives in the decision that lead to a valid parse.
* The predicted alt is the min(ambigAlts)
* @param input The input token stream
* @param startIndex The start index for the current prediction
* @param stopIndex The index at which the ambiguity was identified during
* prediction
* @param fullCtx {@code true} if the ambiguity was identified during LL
* prediction; otherwise, {@code false} if the ambiguity was identified
* during SLL prediction
*/
public AmbiguityInfo(int decision,
ATNConfigSet configs,
BitSet ambigAlts,
TokenStream input, int startIndex, int stopIndex,
boolean fullCtx)
{
super(decision, configs, input, startIndex, stopIndex, fullCtx);
this.ambigAlts = ambigAlts;
}
}