Package net.sf.saxon.regex

Class OpNothing

java.lang.Object

net.sf.saxon.regex.Operation

net.sf.saxon.regex.OpNothing

public class OpNothing
extends Operation

Match empty string within a regular expression

Nested Class Summary

Nested classes/interfaces inherited from class net.sf.saxon.regex.Operation

Operation.ForceProgressIterator

Field Summary

Fields inherited from class net.sf.saxon.regex.Operation

MATCHES_ZLS_ANYWHERE, MATCHES_ZLS_AT_END, MATCHES_ZLS_AT_START, MATCHES_ZLS_NEVER

Constructor Summary

Constructors

Constructor	Description
OpNothing()

Method Summary

Modifier and Type	Method	Description
java.lang.String	display()	Display the operation as a regular expression, possibly in abbreviated form
int	getMatchLength()	Get the length of the matches returned by this operation if they are fixed-length
IntIterator	iterateMatches(REMatcher matcher, int position)	Get an iterator returning all the matches for this operation
int	matchesEmptyString()	Ask whether the regular expression is known, after static analysis, to match a zero-length string

Methods inherited from class net.sf.saxon.regex.Operation

containsCapturingExpressions, getInitialCharacterClass, getMaxLoopingDepth, getMinimumMatchLength, optimize

Methods inherited from class java.lang.Object

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

Constructor Detail

OpNothing

public OpNothing()

Method Detail

iterateMatches

public IntIterator iterateMatches(REMatcher matcher,
                                  int position)

Description copied from class: Operation

Get an iterator returning all the matches for this operation

Specified by:

iterateMatches in class Operation

Parameters:

matcher - supplies the context for the matching; may be updated with information about captured groups

position - the start position to seek a match

Returns:

an iterator returning the endpoints of all matches starting at the supplied position

matchesEmptyString

public int matchesEmptyString()

Description copied from class: Operation

Ask whether the regular expression is known, after static analysis, to match a zero-length string

Specified by:

matchesEmptyString in class Operation

Returns:

a value indicating whether the regex is statically known to match a zero-length string. Specifically:

• returns Operation.MATCHES_ZLS_AT_START if the expression is statically known to match a zero-length string at the start of the supplied input;
• returns Operation.MATCHES_ZLS_AT_END if it is statically known to return a zero-length string at the end of the supplied input;
• returns Operation.MATCHES_ZLS_ANYWHERE if it is statically known to match a zero-length string anywhere in the input.
• returns Operation.MATCHES_ZLS_NEVER if it is statically known that the regex will never match a zero length string.

Returning 0 means that it is not known statically whether or not the regex will match a zero-length string; this case typically arises when back-references are involved.

getMatchLength

public int getMatchLength()

Description copied from class: Operation

Get the length of the matches returned by this operation if they are fixed-length

Overrides:

getMatchLength in class Operation

Returns:

the length of the matches, or -1 if the length is variable

display

public java.lang.String display()

Display the operation as a regular expression, possibly in abbreviated form

Specified by:

display in class Operation

Returns:

the operation in a form that is recognizable as a regular expression or abbreviated regular expression