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:

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
complexp	::=	~ complexp	(complement)	[OPTIONAL]
	|	charclassexp
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)
	|	\ <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.

Field Summary

Fields

Modifier and Type	Field and Description
static int	ALL Syntax flag, enables all optional regexp syntax.
static int	ANYSTRING Syntax flag, enables anystring (@).
static int	AUTOMATON Syntax flag, enables named automata (<identifier>).
static int	COMPLEMENT Syntax flag, enables complement (~).
static int	EMPTY Syntax flag, enables empty language (#).
static int	INTERSECTION Syntax flag, enables intersection (&).
static int	INTERVAL Syntax flag, enables numerical intervals ( <n-m>).
static int	NONE Syntax flag, enables no optional regexp syntax.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and 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(AutomatonProvider automaton_provider, int maxDeterminizedStates) Constructs new Automaton from this RegExp.
Automaton	toAutomaton(int maxDeterminizedStates) Constructs new Automaton from this RegExp.
Automaton	toAutomaton(Map<String,Automaton> automata, int maxDeterminizedStates) 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 Detail

INTERSECTION

public static final int INTERSECTION

Syntax flag, enables intersection (&).

See Also:

Constant Field Values

COMPLEMENT

public static final int COMPLEMENT

Syntax flag, enables complement (~).

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

Constructor Detail

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 occured 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 occured while parsing the regular expression

Method Detail

toAutomaton

public Automaton toAutomaton()

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

toAutomaton

public Automaton toAutomaton(int maxDeterminizedStates)
                      throws IllegalArgumentException,
                             TooComplexToDeterminizeException

Constructs new Automaton from this RegExp. The constructed automaton is minimal and deterministic and has no transitions to dead states.

Parameters:

maxDeterminizedStates - maximum number of states in the resulting automata. If the automata would need more than this many states TooComplextToDeterminizeException is thrown. Higher number require more space but can process more complex regexes.

Throws:

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

TooComplexToDeterminizeException - if determinizing this regexp requires more than maxDeterminizedStates states

toAutomaton

public Automaton toAutomaton(AutomatonProvider automaton_provider,
                             int maxDeterminizedStates)
                      throws IllegalArgumentException,
                             TooComplexToDeterminizeException

Constructs new Automaton from this RegExp. The constructed automaton is minimal and deterministic and has no transitions to dead states.

Parameters:

automaton_provider - provider of automata for named identifiers

maxDeterminizedStates - maximum number of states in the resulting automata. If the automata would need more than this many states TooComplextToDeterminizeException is thrown. Higher number require more space but can process more complex regexes.

Throws:

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

TooComplexToDeterminizeException - if determinizing this regexp requires more than maxDeterminizedStates states

toAutomaton

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

Constructs new Automaton from this RegExp. The constructed automaton is minimal and deterministic and has no transitions to dead states.

Parameters:

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

maxDeterminizedStates - maximum number of states in the resulting automata. If the automata would need more than this many states TooComplexToDeterminizeException is thrown. Higher number require more space but can process more complex regexes.

Throws:

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

TooComplexToDeterminizeException - if determinizing this regexp requires more than maxDeterminizedStates states

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.