Package org.apache.lucene.util.automaton

Class RegExp

java.lang.Object

org.apache.lucene.util.automaton.RegExp

public class RegExp
extends Object

Regular Expression extension to Automaton.

Regular expressions are built from the following abstract syntax:

description of regular expression grammar

regexp	::=	unionexp
	|
unionexp	::=	interexp | unionexp	(union)
	|	interexp
interexp	::=	concatexp & interexp	(intersection)	[OPTIONAL]
	|	concatexp
concatexp	::=	repeatexp concatexp	(concatenation)
	|	repeatexp
repeatexp	::=	repeatexp ?	(zero or one occurrence)
	|	repeatexp *	(zero or more occurrences)
	|	repeatexp +	(one or more occurrences)
	|	repeatexp {n}	(n occurrences)
	|	repeatexp {n,}	(n or more occurrences)
	|	repeatexp {n,m}	(n to m occurrences, including both)
	|	complexp
charclassexp	::=	[ charclasses ]	(character class)
	|	[^ charclasses ]	(negated character class)
	|	simpleexp
charclasses	::=	charclass charclasses
	|	charclass
charclass	::=	charexp - charexp	(character range, including end-points)
	|	charexp
simpleexp	::=	charexp
	|	.	(any single character)
	|	#	(the empty language)	[OPTIONAL]
	|	@	(any string)	[OPTIONAL]
	|	" <Unicode string without double-quotes> "	(a string)
	|	( )	(the empty string)
	|	( unionexp )	(precedence override)
	|	< <identifier> >	(named automaton)	[OPTIONAL]
	|	<n-m>	(numerical interval)	[OPTIONAL]
charexp	::=	<Unicode character>	(a single non-reserved character)
	|	\d	(a digit [0-9])
	|	\D	(a non-digit [^0-9])
	|	\s	(whitespace [ \t\n\r])
	|	\S	(non whitespace [^\s])
	|	\w	(a word character [a-zA-Z_0-9])
	|	\W	(a non word character [^\w])
	|	\ <Unicode character>	(a single character)

The productions marked [OPTIONAL] are only allowed if specified by the syntax flags passed to the RegExp constructor. The reserved characters used in the (enabled) syntax must be escaped with backslash (\) or double-quotes ( "..."). (In contrast to other regexp syntaxes, this is required also in character classes.) Be aware that dash (-) has a special meaning in charclass expressions. An identifier is a string not containing right angle bracket (> ) or dash (-). Numerical intervals are specified by non-negative decimal integers and include both end points, and if n and m have the same number of digits, then the conforming strings must have that length (i.e. prefixed by 0's).

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	RegExp.Kind	The type of expression represented by a RegExp node.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	ALL	Syntax flag, enables all optional regexp syntax.
static final int	ANYSTRING	Syntax flag, enables anystring (@).
static final int	ASCII_CASE_INSENSITIVE	Allows case insensitive matching of ASCII characters.
static final int	AUTOMATON	Syntax flag, enables named automata (<identifier>).
final int	c	Character expression
static final int	DEPRECATED_COMPLEMENT	Deprecated. This method will be removed in Lucene 11
final int	digits	Limits for repeatable type expressions
static final int	EMPTY	Syntax flag, enables empty language (#).
final RegExp	exp1	Child expressions held by a container type expression
final RegExp	exp2	Child expressions held by a container type expression
final int	from	Extents for range type expressions
static final int	INTERSECTION	Syntax flag, enables intersection (&).
static final int	INTERVAL	Syntax flag, enables numerical intervals ( <n-m>).
final RegExp.Kind	kind	The type of expression
final int	max	Limits for repeatable type expressions
final int	min	Limits for repeatable type expressions
static final int	NONE	Syntax flag, enables no optional regexp syntax.
final String	s	String expression
final int	to	Extents for range type expressions

Constructor Summary

Constructors

Constructor	Description
RegExp(String s)	Constructs new RegExp from a string.
RegExp(String s, int syntax_flags)	Constructs new RegExp from a string.
RegExp(String s, int syntax_flags, int match_flags)	Constructs new RegExp from a string.

Method Summary

Modifier and Type	Method	Description
Set<String>	getIdentifiers()	Returns set of automaton identifiers that occur in this regular expression.
String	getOriginalString()	The string that was used to construct the regex.
Automaton	toAutomaton()	Constructs new Automaton from this RegExp.
Automaton	toAutomaton(Map<String,Automaton> automata)	Constructs new Automaton from this RegExp.
Automaton	toAutomaton(AutomatonProvider automaton_provider)	Constructs new Automaton from this RegExp.
String	toString()	Constructs string from parsed regular expression.
String	toStringTree()	Like to string, but more verbose (shows the higherchy more clearly).

Methods inherited from class java.lang.Object

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

Field Details

INTERSECTION

public static final int INTERSECTION

Syntax flag, enables intersection (&).

See Also:

• Constant Field Values

EMPTY

public static final int EMPTY

Syntax flag, enables empty language (#).

See Also:

• Constant Field Values

ANYSTRING

public static final int ANYSTRING

Syntax flag, enables anystring (@).

See Also:

• Constant Field Values

AUTOMATON

public static final int AUTOMATON

Syntax flag, enables named automata (<identifier>).

See Also:

• Constant Field Values

INTERVAL

public static final int INTERVAL

Syntax flag, enables numerical intervals ( <n-m>).

See Also:

• Constant Field Values

ALL

public static final int ALL

Syntax flag, enables all optional regexp syntax.

See Also:

• Constant Field Values

NONE

public static final int NONE

Syntax flag, enables no optional regexp syntax.

See Also:

• Constant Field Values

ASCII_CASE_INSENSITIVE

public static final int ASCII_CASE_INSENSITIVE

Allows case insensitive matching of ASCII characters.

See Also:

• Constant Field Values

DEPRECATED_COMPLEMENT

@Deprecated
public static final int DEPRECATED_COMPLEMENT

Deprecated.

This method will be removed in Lucene 11

Allows regexp parsing of the complement (~).

Note that processing the complement can require exponential time, but will be bounded by an internal limit. Regexes exceeding the limit will fail with TooComplexToDeterminizeException.

See Also:

• Constant Field Values

kind

public final RegExp.Kind kind

The type of expression

exp1

public final RegExp exp1

Child expressions held by a container type expression

exp2

public final RegExp exp2

Child expressions held by a container type expression

s

public final String s

String expression

c

public final int c

Character expression

min

public final int min

Limits for repeatable type expressions

max

public final int max

Limits for repeatable type expressions

digits

public final int digits

Limits for repeatable type expressions

from

public final int from

Extents for range type expressions

to

public final int to

Extents for range type expressions

Constructor Details

RegExp

public RegExp(String s)
       throws IllegalArgumentException

Constructs new RegExp from a string. Same as RegExp(s, ALL).

Parameters:

s - regexp string

Throws:

IllegalArgumentException - if an error occurred while parsing the regular expression

RegExp

public RegExp(String s,
 int syntax_flags)
       throws IllegalArgumentException

Constructs new RegExp from a string.

Parameters:

s - regexp string

syntax_flags - boolean 'or' of optional syntax constructs to be enabled

Throws:

IllegalArgumentException - if an error occurred while parsing the regular expression

RegExp

public RegExp(String s,
 int syntax_flags,
 int match_flags)
       throws IllegalArgumentException

Constructs new RegExp from a string.

Parameters:

s - regexp string

syntax_flags - boolean 'or' of optional syntax constructs to be enabled

match_flags - boolean 'or' of match behavior options such as case insensitivity

Throws:

IllegalArgumentException - if an error occurred while parsing the regular expression

Method Details

toAutomaton

public Automaton toAutomaton()

Constructs new Automaton from this RegExp. Same as toAutomaton(null) (empty automaton map).

toAutomaton

public Automaton toAutomaton(AutomatonProvider automaton_provider)
                      throws IllegalArgumentException,
TooComplexToDeterminizeException

Constructs new Automaton from this RegExp.

Parameters:

automaton_provider - provider of automata for named identifiers

Throws:

IllegalArgumentException - if this regular expression uses a named identifier that is not available from the automaton provider

TooComplexToDeterminizeException

toAutomaton

public Automaton toAutomaton(Map<String,Automaton> automata)
                      throws IllegalArgumentException,
TooComplexToDeterminizeException

Constructs new Automaton from this RegExp.

Parameters:

automata - a map from automaton identifiers to automata (of type Automaton).

Throws:

IllegalArgumentException - if this regular expression uses a named identifier that does not occur in the automaton map

TooComplexToDeterminizeException

getOriginalString

public String getOriginalString()

The string that was used to construct the regex. Compare to toString.

toString

public String toString()

Constructs string from parsed regular expression.

Overrides:

toString in class Object

toStringTree

public String toStringTree()

Like to string, but more verbose (shows the higherchy more clearly).

getIdentifiers

public Set<String> getIdentifiers()

Returns set of automaton identifiers that occur in this regular expression.