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

Class CalcMinPathsVisitor

java.lang.Object

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

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

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

public class CalcMinPathsVisitor
extends DepthFirstTraversalRegexASTVisitor

This visitor will set the RegexASTNode.getMinPath() - property of children of an AST in the following manner:

• The minPath of LookBehindAssertion and LookAheadAssertion nodes is the minimum number of CharacterClass nodes that need to be traversed in order to reach the node.
• The minPath of BackReference, PositionAssertion and MatchFound nodes is undefined (or is always 0). Their minPath is never set by CalcMinPathsVisitor.
• The minPath of Sequence and Group nodes is the minimum number of CharacterClass nodes that need to be traversed in order to reach the end of the node. The minPath field of Sequence nodes is used as a mutable iteration variable when traversing their children (see CalcMinPathsVisitor.visit(CharacterClass)). The resulting value after the traversal holds the minimum number of CharacterClass nodes that need to be traversed to reach the end of the Sequence. The same holds for Group nodes.

CalcMinPathsVisitor will also set RegexASTNode.getMaxPath(), analogous to RegexASTNode.getMinPath(), but without taking loops (Group.isLoop()) into account. CalcMinPathsVisitor will simultaneously mark PositionAssertions (type PositionAssertion.Type.CARET in forward mode and PositionAssertion.Type.DOLLAR in backward mode) whose minimum path is greater than zero as dead. Note that this algorithm will e.g. not mark the dollar assertion in /(?=a$)bc/ as dead, since it has a (reverse) minimum path of 0 inside the look-ahead assertion. The visitor will also mark all Sequence nodes that start with a caret PositionAssertion or end with a dollar PositionAssertion with the RegexASTNode.startsWithCaret()/RegexASTNode.endsWithDollar() flags, and likewise for all Groups where all child Sequences start with a caret or end with a dollar. The visitor is intended to be run on an AST once in reverse, and then once in forward direction. The results of the forward run will be used by RegexAST.createPrefix().

See Also:

RegexASTNode.startsWithCaret(), RegexASTNode.endsWithDollar(), RegexASTNode.getMinPath(), RegexASTNode.getMaxPath(), RegexASTNode.isDead(), RegexAST.createPrefix()

Constructor Summary

Constructors

Constructor and Description
CalcMinPathsVisitor()

Method Summary

Modifier and Type	Method and Description
protected void	init(RegexASTNode runRoot)
protected void	leave(Group group)
protected void	leave(LookAheadAssertion assertion)
protected void	leave(LookBehindAssertion assertion)
void	leaveLookAroundAssertion(LookAroundAssertion assertion)
protected void	visit(BackReference backReference)
protected void	visit(CharacterClass characterClass)
protected void	visit(Group group)
protected void	visit(LookAheadAssertion assertion)
protected void	visit(LookBehindAssertion assertion)
protected void	visit(MatchFound matchFound)
protected void	visit(PositionAssertion assertion)
protected void	visit(Sequence sequence)

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

isReverse, leave, run, runReverse

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

doLeave, doVisit

Methods inherited from class java.lang.Object

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

Constructor Detail

CalcMinPathsVisitor

public CalcMinPathsVisitor()

Method Detail

init

protected void init(RegexASTNode runRoot)

Overrides:

init in class DepthFirstTraversalRegexASTVisitor

visit

protected void visit(BackReference backReference)

Overrides:

visit in class DepthFirstTraversalRegexASTVisitor

visit

protected void visit(Group group)

Overrides:

visit in class DepthFirstTraversalRegexASTVisitor

leave

protected void leave(Group group)

Overrides:

leave in class DepthFirstTraversalRegexASTVisitor

visit

protected void visit(Sequence sequence)

Overrides:

visit in class DepthFirstTraversalRegexASTVisitor

visit

protected void visit(PositionAssertion assertion)

Overrides:

visit in class DepthFirstTraversalRegexASTVisitor

visit

protected void visit(LookBehindAssertion assertion)

Overrides:

visit in class DepthFirstTraversalRegexASTVisitor

leave

protected void leave(LookBehindAssertion assertion)

Overrides:

leave in class DepthFirstTraversalRegexASTVisitor

visit

protected void visit(LookAheadAssertion assertion)

Overrides:

visit in class DepthFirstTraversalRegexASTVisitor

leave

protected void leave(LookAheadAssertion assertion)

Overrides:

leave in class DepthFirstTraversalRegexASTVisitor

leaveLookAroundAssertion

public void leaveLookAroundAssertion(LookAroundAssertion assertion)

visit

protected void visit(CharacterClass characterClass)

Overrides:

visit in class DepthFirstTraversalRegexASTVisitor

visit

protected void visit(MatchFound matchFound)

Overrides:

visit in class DepthFirstTraversalRegexASTVisitor