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

Class LookBehindAssertion

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

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

All Implemented Interfaces:

IndexedState, RegexASTVisitorIterable, JsonConvertible

public class LookBehindAssertion
extends LookAroundAssertion

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

Corresponds to the ( ? <= Disjunction ) and ( ? <! Disjunction ) right-hand sides of the Assertion goal symbol in the ECMAScript RegExp syntax.

Currently, the fragment of regular expressions that TRegex supports in lookbehind assertions is limited to so-called "literal" regular expressions, consisting only of concatenations and character classes (which generalize literal characters). The method LookBehindAssertion.isLiteral() verifies whether the body of the assertion (RegexASTSubtreeRootNode.getGroup()) is of this form.

Field Summary

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

FLAG_CHARACTER_CLASS_WAS_SINGLE_CHAR, FLAG_EMPTY_GUARD, FLAG_GROUP_EXPANDED_QUANTIFIER, FLAG_GROUP_LOOP, FLAG_HAS_LOOPS, FLAG_LOOK_AROUND_NEGATED

Method Summary

Modifier and Type	Method and Description
LookBehindAssertion	copy(RegexAST ast, boolean recursive) Copy this node, in one of the following ways: if recursive is true, recursively copy this subtree.
boolean	equalsSemantic(RegexASTNode obj, boolean ignoreQuantifier)
int	getLength() Returns the length of the words that can be matched by the body of this lookbehind assertion.
String	getPrefix()
boolean	isLiteral() Verifies that the contents of this assertion (RegexASTSubtreeRootNode.getGroup()) are in "literal" form.
JsonValue	toJson()

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

isNegated, setNegated

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

getGroup, getMatchFound, resetVisitorIterator, setGroup, setMatchFound, toJson, toString, visitorGetNext, visitorHasNext

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

equalsSemantic, getQuantifier, getSeqIndex, getSubTreeParent, hasQuantifier, quantifierToString, setQuantifier, setSeqIndex

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

astNodeId, endsWithDollar, getId, getMaxPath, getMinPath, getParent, hasEmptyGuard, hasLoops, idInitialized, incMaxPath, incMaxPath, incMinPath, incMinPath, isDead, isFlagSet, isInLookAheadAssertion, isInLookBehindAssertion, isPrefix, markAsDead, setEmptyGuard, setEndsWithDollar, setEndsWithDollar, setFlag, setFlag, setHasLoops, setHasLoops, setId, setMaxPath, setMinPath, setParent, setPrefix, setStartsWithCaret, setStartsWithCaret, startsWithCaret, toStringWithID

Methods inherited from class java.lang.Object

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

Method Detail

copy

public LookBehindAssertion copy(RegexAST ast,
                                boolean recursive)

Description copied from class: RegexASTNode

Copy this node, in one of the following ways:

• if recursive is true, recursively copy this subtree. This method should be used instead of CopyVisitor if the copying process is required to be thread-safe.
• else, copy this node only, without any child nodes.

In both cases, the ID and minPath of the copied nodes is left unset.

Specified by:

copy in class RegexASTSubtreeRootNode

Parameters:

ast - RegexAST the new nodes should belong to.

Returns:

A shallow or deep copy of this node.

isLiteral

public boolean isLiteral()

Verifies that 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 and terminated by a MatchFound node.

getLength

public int getLength()

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.

getPrefix

public String getPrefix()

Specified by:

getPrefix in class RegexASTSubtreeRootNode

equalsSemantic

public boolean equalsSemantic(RegexASTNode obj,
                              boolean ignoreQuantifier)

Specified by:

equalsSemantic in class Term

toJson

public JsonValue toJson()