org.antlr.v4.runtime

Class ParserInterpreter

java.lang.Object

org.antlr.v4.runtime.Recognizer<Token,ParserATNSimulator>

org.antlr.v4.runtime.Parser

org.antlr.v4.runtime.ParserInterpreter

public class ParserInterpreter
extends Parser

A parser simulator that mimics what ANTLR's generated parser code does. A ParserATNSimulator is used to make predictions via adaptivePredict but this class moves a pointer through the ATN to simulate parsing. ParserATNSimulator just makes us efficient rather than having to backtrack, for example. This properly creates parse trees even for left recursive rules. We rely on the left recursive rule invocation and special predicate transitions to make left recursive rules work. See TestParserInterpreter for examples.

Nested Class Summary

Nested classes/interfaces inherited from class org.antlr.v4.runtime.Parser

Parser.TraceListener, Parser.TrimToSizeListener

Field Summary

Fields

Modifier and Type	Field and Description
protected Deque<Tuple2<ParserRuleContext,Integer>>	_parentContextStack Tracks LR rules for adjusting the contexts
protected ATN	atn
protected String	grammarFileName
protected int	overrideDecision We need a map from (decision,inputIndex)->forced alt for computing ambiguous parse trees.
protected int	overrideDecisionAlt
protected int	overrideDecisionInputIndex
protected BitSet	pushRecursionContextStates This identifies StarLoopEntryState's that begin the (...)* precedence loops of left recursive rules.
protected String[]	ruleNames
protected String[]	tokenNames Deprecated.

Fields inherited from class org.antlr.v4.runtime.Parser

_buildParseTrees, _ctx, _errHandler, _input, _parseListeners, _precedenceStack, _syntaxErrors

Fields inherited from class org.antlr.v4.runtime.Recognizer

_interp, EOF

Constructor Summary

Constructors

Constructor and Description
ParserInterpreter(ParserInterpreter old) A copy constructor that creates a new parser interpreter by reusing the fields of a previous interpreter.
ParserInterpreter(String grammarFileName, Collection<String> tokenNames, Collection<String> ruleNames, ATN atn, TokenStream input) Deprecated. Use ParserInterpreter(String, Vocabulary, Collection, ATN, TokenStream) instead.
ParserInterpreter(String grammarFileName, Vocabulary vocabulary, Collection<String> ruleNames, ATN atn, TokenStream input)

Method Summary

Methods

Modifier and Type	Method and Description
void	addDecisionOverride(int decision, int tokenIndex, int forcedAlt) Override this parser interpreters normal decision-making process at a particular decision and input token index.
void	enterRecursionRule(ParserRuleContext localctx, int state, int ruleIndex, int precedence)
ATN	getATN() Get the ATN used by the recognizer for prediction.
protected ATNState	getATNState()
String	getGrammarFileName() For debugging and other purposes, might want the grammar name.
String[]	getRuleNames()
String[]	getTokenNames() Deprecated.
Vocabulary	getVocabulary() Get the vocabulary used by the recognizer.
ParserRuleContext	parse(int startRuleIndex) Begin parsing at startRuleIndex
protected void	visitRuleStopState(ATNState p)
protected void	visitState(ATNState p)

Methods inherited from class org.antlr.v4.runtime.Parser

addContextToParseTree, addParseListener, compileParseTreePattern, compileParseTreePattern, consume, dumpDFA, enterLeftFactoredRule, enterOuterAlt, enterRecursionRule, enterRule, exitRule, getAmbiguousParseTrees, getATNWithBypassAlts, getBuildParseTree, getContext, getCurrentToken, getDFAStrings, getErrorHandler, getErrorListenerDispatch, getExpectedTokens, getExpectedTokensWithinCurrentRule, getInputStream, getInvokingContext, getNumberOfSyntaxErrors, getParseInfo, getParseListeners, getPrecedence, getRuleContext, getRuleIndex, getRuleInvocationStack, getRuleInvocationStack, getSourceName, getTokenFactory, getTrimParseTree, inContext, isExpectedToken, isTrace, match, matchWildcard, notifyErrorListeners, notifyErrorListeners, precpred, pushNewRecursionContext, removeParseListener, removeParseListeners, reset, setBuildParseTree, setContext, setErrorHandler, setInputStream, setProfile, setTrace, setTrimParseTree, triggerEnterRuleEvent, triggerExitRuleEvent, unrollRecursionContexts

Methods inherited from class org.antlr.v4.runtime.Recognizer

action, addErrorListener, getErrorHeader, getErrorListeners, getInterpreter, getRuleIndexMap, getSerializedATN, getState, getTokenErrorDisplay, getTokenType, getTokenTypeMap, removeErrorListener, removeErrorListeners, sempred, setInterpreter, setState

Methods inherited from class java.lang.Object

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

Field Detail

grammarFileName

protected final String grammarFileName

atn

protected final ATN atn

pushRecursionContextStates

protected final BitSet pushRecursionContextStates

This identifies StarLoopEntryState's that begin the (...)* precedence loops of left recursive rules.

tokenNames

@Deprecated
protected final String[] tokenNames

Deprecated.

ruleNames

protected final String[] ruleNames

_parentContextStack

protected final Deque<Tuple2<ParserRuleContext,Integer>> _parentContextStack

Tracks LR rules for adjusting the contexts

overrideDecision

protected int overrideDecision

We need a map from (decision,inputIndex)->forced alt for computing ambiguous parse trees. For now, we allow exactly one override.

overrideDecisionInputIndex

protected int overrideDecisionInputIndex

overrideDecisionAlt

protected int overrideDecisionAlt

Constructor Detail

ParserInterpreter

public ParserInterpreter(@NotNull
                 ParserInterpreter old)

A copy constructor that creates a new parser interpreter by reusing the fields of a previous interpreter.

Parameters:

old - The interpreter to copy

Since:

4.5

ParserInterpreter

@Deprecated
public ParserInterpreter(String grammarFileName,
                            Collection<String> tokenNames,
                            Collection<String> ruleNames,
                            ATN atn,
                            TokenStream input)

Deprecated. Use ParserInterpreter(String, Vocabulary, Collection, ATN, TokenStream) instead.

ParserInterpreter

public ParserInterpreter(String grammarFileName,
                 @NotNull
                 Vocabulary vocabulary,
                 Collection<String> ruleNames,
                 ATN atn,
                 TokenStream input)

Method Detail

getATN

public ATN getATN()

Description copied from class: Recognizer

Get the ATN used by the recognizer for prediction.

Overrides:

getATN in class Recognizer<Token,ParserATNSimulator>

Returns:

The ATN used by the recognizer for prediction.

getTokenNames

@Deprecated
public String[] getTokenNames()

Deprecated.

Description copied from class: Recognizer

Used to print out token names like ID during debugging and error reporting. The generated parsers implement a method that overrides this to point to their String[] tokenNames.

Specified by:

getTokenNames in class Recognizer<Token,ParserATNSimulator>

getVocabulary

public Vocabulary getVocabulary()

Description copied from class: Recognizer

Get the vocabulary used by the recognizer.

Overrides:

getVocabulary in class Recognizer<Token,ParserATNSimulator>

Returns:

A Vocabulary instance providing information about the vocabulary used by the grammar.

getRuleNames

public String[] getRuleNames()

Specified by:

getRuleNames in class Recognizer<Token,ParserATNSimulator>

getGrammarFileName

public String getGrammarFileName()

Description copied from class: Recognizer

For debugging and other purposes, might want the grammar name. Have ANTLR generate an implementation for this method.

Specified by:

getGrammarFileName in class Recognizer<Token,ParserATNSimulator>

parse

public ParserRuleContext parse(int startRuleIndex)

Begin parsing at startRuleIndex

enterRecursionRule

public void enterRecursionRule(ParserRuleContext localctx,
                      int state,
                      int ruleIndex,
                      int precedence)

Overrides:

enterRecursionRule in class Parser

getATNState

protected ATNState getATNState()

visitState

protected void visitState(ATNState p)

visitRuleStopState

protected void visitRuleStopState(ATNState p)

addDecisionOverride

public void addDecisionOverride(int decision,
                       int tokenIndex,
                       int forcedAlt)

Override this parser interpreters normal decision-making process at a particular decision and input token index. Instead of allowing the adaptive prediction mechanism to choose the first alternative within a block that leads to a successful parse, force it to take the alternative, 1..n for n alternatives. As an implementation limitation right now, you can only specify one override. This is sufficient to allow construction of different parse trees for ambiguous input. It means re-parsing the entire input in general because you're never sure where an ambiguous sequence would live in the various parse trees. For example, in one interpretation, an ambiguous input sequence would be matched completely in expression but in another it could match all the way back to the root. s : e '!'? ; e : ID | ID '!' ; Here, x! can be matched as (s (e ID) !) or (s (e ID !)). In the first case, the ambiguous sequence is fully contained only by the root. In the second case, the ambiguous sequences fully contained within just e, as in: (e ID !). Rather than trying to optimize this and make some intelligent decisions for optimization purposes, I settled on just re-parsing the whole input and then using {link Trees#getRootOfSubtreeEnclosingRegion} to find the minimal subtree that contains the ambiguous sequence. I originally tried to record the call stack at the point the parser detected and ambiguity but left recursive rules create a parse tree stack that does not reflect the actual call stack. That impedance mismatch was enough to make it it challenging to restart the parser at a deeply nested rule invocation. Only parser interpreters can override decisions so as to avoid inserting override checking code in the critical ALL(*) prediction execution path.

Since:

4.5