Class LookAroundAssertion

java.lang.Object

com.oracle.truffle.regex.tregex.parser.ast.RegexASTNode

com.oracle.truffle.regex.tregex.parser.ast.Term

com.oracle.truffle.regex.tregex.parser.ast.RegexASTSubtreeRootNode

com.oracle.truffle.regex.tregex.parser.ast.LookAroundAssertion

All Implemented Interfaces:

AbstractState<Term,ASTTransition>, RegexASTVisitorIterable, JsonConvertible

Direct Known Subclasses:

LookAheadAssertion, LookBehindAssertion

public abstract class LookAroundAssertion
extends RegexASTSubtreeRootNode

An assertion that succeeds depending on whether or not text surrounding the current position matches a given regular expression.

See its two subclasses, LookAheadAssertion and LookBehindAssertion.

Method Summary

Modifier and Type	Method	Description
boolean	endsWithCharClass()
int	getLiteralLength()	Returns the length of the words that can be matched by the body of this lookbehind assertion.
boolean	isLiteral()	Checks if the contents of this assertion (RegexASTSubtreeRootNode.getGroup()) are in "literal" form.
boolean	isNegated()	Indicates whether this is a negative lookaround assertion (written as (?!...) (?<!...)) or a positive one (written as (?=...) or (?<=)).
boolean	isSingleCCNonCapturingLiteral()	Returns true iff this is a literal of size 1, without any capturing groups.
void	setNegated(boolean negated)
boolean	startsWithCharClass()

Methods inherited from class com.oracle.truffle.regex.tregex.parser.ast.RegexASTSubtreeRootNode

copy, getAnchoredFinalState, getAnchoredInitialState, getGlobalSubTreeId, getGroup, getMatchFound, getPrefix, getSubTreeId, getSubtrees, getUnAnchoredInitialState, globalSubTreeIdInitialized, resetVisitorIterator, setAnchoredFinalState, setAnchoredInitialState, setGlobalSubTreeId, setGroup, setMatchFound, setSubTreeId, setUnAnchoredInitialState, subTreeIdInitialized, toJson, toString, visitorGetNext, visitorHasNext

Methods inherited from class com.oracle.truffle.regex.tregex.parser.ast.Term

copyRecursive, getSeqIndex, getSubTreeParent, setSeqIndex

Methods inherited from class com.oracle.truffle.regex.tregex.parser.ast.RegexASTNode

asAtomicGroup, asBackReference, asCharacterClass, asConditionalBackReferenceGroup, asGroup, asLookAheadAssertion, asLookAroundAssertion, asLookBehindAssertion, asMatchFound, asPositionAssertion, asQuantifiableTerm, asSequence, asSubexpressionCall, asSubtreeRootNode, astNodeId, endsWithDollar, equalsSemantic, getFlags, getId, getMaxPath, getMinPath, getParent, getPrefixLengthMax, getPrefixLengthMin, hasBackReferences, hasCaptureGroups, hasCaret, hasDollar, hasEmptyGuard, hasLookAheads, hasLookBehinds, hasLoops, hasQuantifiers, hasVariablePrefixLength, idInitialized, incMaxPath, incMaxPath, incMinPath, incMinPath, isAtomicGroup, isBackReference, isCaret, isCharacterClass, isConditionalBackReferenceGroup, isDead, isDollar, isExpandedQuantifier, isFlagSet, isGroup, isGroupWithGuards, isInLookAheadAssertion, isInLookBehindAssertion, isLookAheadAssertion, isLookAroundAssertion, isLookBehindAssertion, isMandatoryUnrolledQuantifier, isMatchFound, isPositionAssertion, isPrefix, isQuantifiableTerm, isQuantifierPassThroughSequence, isRoot, isSequence, isSubexpressionCall, isSubtreeRoot, markAsDead, setDead, setEmptyGuard, setEndsWithDollar, setEndsWithDollar, setExpandedQuantifier, setFlag, setFlag, setFlags, setHasBackReferences, setHasCaptureGroups, setHasCaret, setHasCaret, setHasDollar, setHasDollar, setHasLookAheads, setHasLookBehinds, setHasLoops, setHasLoops, setHasQuantifiers, setId, setMandatoryUnrolledQuantifier, setMaxPath, setMinPath, setParent, setPrefix, setPrefixLengthMax, setPrefixLengthMin, setQuantifierPassThroughSequence, setStartsWithCaret, setStartsWithCaret, startsWithCaret, toStringWithID

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.oracle.truffle.regex.tregex.automaton.AbstractState

getId

Methods inherited from interface com.oracle.truffle.regex.tregex.util.json.JsonConvertible

toJson

Method Details

isNegated

public boolean isNegated()

Indicates whether this is a negative lookaround assertion (written as (?!...) (?<!...)) or a positive one (written as (?=...) or (?<=)).

Positive lookaround assertions match if and only if the text around the current position matches the contents of the assertion. Negative lookaround assertions match if and only if the text around the current position does not match the contents of the assertion.

setNegated

public void setNegated(boolean negated)

startsWithCharClass

public boolean startsWithCharClass()

endsWithCharClass

public boolean endsWithCharClass()

isLiteral

public boolean isLiteral()

Checks if the contents of this assertion (RegexASTSubtreeRootNode.getGroup()) are in "literal" form. This means that there is only a single alternative which is composed of a sequence of CharacterClass nodes.

getLiteralLength

public int getLiteralLength()

Returns the length of the words that can be matched by the body of this lookbehind assertion.

Because we restrict the regular expressions used in lookbehind assertions to "literal" regular expressions, all strings that match the body of the assertion are guaranteed to be of the same length. This is critical to how lookbehind is implemented, because it tells us how much do we have to rewind when matching a regular expression with lookbehind assertions.

isSingleCCNonCapturingLiteral

public boolean isSingleCCNonCapturingLiteral()

Returns true iff this is a literal of size 1, without any capturing groups.