de.up.ling.irtg.algebra

Class StringAlgebra

java.lang.Object

de.up.ling.irtg.algebra.Algebra<List<String>>

de.up.ling.irtg.algebra.StringAlgebra

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

WideStringAlgebra

public class StringAlgebra
extends Algebra<List<String>>
implements Serializable

The binary string algebra. The elements of this algebra are lists of strings, which can be thought of as the words in a sentence. The algebra has a single binary operation symbol, *, which evaluates to string concatenation. All other strings are nullary symbols of this algebra; the string w evaluates to the list [w] .

Notice that the algebra's signature is made aware of these nullary symbols only when parseString(java.lang.String) sees these symbols. This means that the contents of the signature may change as more string representations are parsed.

Author:

koller

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	StringAlgebra.Span This class is used to represent a sub-span of an input string via its beginning and end index.

Field Summary

Fields

Modifier and Type	Field and Description
static String	CONCAT The reserved concatenation symbol used by this algebra.
static String	SPECIAL_STAR A special symbol in the algebra that represents a terminal "*" which we cannot represent directly, it is interpreted as [*].

Constructor Summary

Constructors

Constructor and Description
StringAlgebra() Creates a new instance with a new signature.

Method Summary

Modifier and Type	Method and Description
TreeAutomaton	decompose(List<String> words) Computes a decomposition automaton for the given value.
List<String>	evaluate(Tree<String> t) Evaluates a term over the algebra's signature into an algebra object.
String	getBinaryConcatenation() Returns the concatenation symbol for this algebra.
Class	getClassOfValues() Returns the class of the elements of this algebra.
static int	getMaxChartSize(int sentenceLength)
static int	getSentenceLength(List<String> sentence)
List<String>	parseString(String representation) Resolves the string representation of some element of the algebra's domain to this element.
String	representAsString(List<String> object) Returns a string representation of this object.

Methods inherited from class de.up.ling.irtg.algebra.Algebra

getAllAlgebraClasses, getSignature, hasOptions, readOptions, setOptions, visualize, writeOptions

Methods inherited from class java.lang.Object

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

Field Detail

CONCAT

public static final String CONCAT

The reserved concatenation symbol used by this algebra.

See Also:

Constant Field Values

SPECIAL_STAR

public static final String SPECIAL_STAR

A special symbol in the algebra that represents a terminal "*" which we cannot represent directly, it is interpreted as [*].

See Also:

Constant Field Values

Constructor Detail

StringAlgebra

public StringAlgebra()

Creates a new instance with a new signature.

Method Detail

evaluate

public List<String> evaluate(Tree<String> t)

Description copied from class: Algebra

Evaluates a term over the algebra's signature into an algebra object.

Overrides:

evaluate in class Algebra<List<String>>

Parameters:

t - a term (= tree whose nodes are labeled with algebra operation symbols)

Returns:

decompose

public TreeAutomaton decompose(List<String> words)

Description copied from class: Algebra

Computes a decomposition automaton for the given value. A decomposition automaton is a finite tree automaton which accepts exactly those terms over the algebra's signature which evaluate to the given value.

Overrides:

decompose in class Algebra<List<String>>

Returns:

getClassOfValues

public Class getClassOfValues()

Description copied from class: Algebra

Returns the class of the elements of this algebra. The default interpretation simply returns Object; you may override this with the actual class of the objects of your algebra.

This method is used in some places throughout Alto to figure out what OutputCodecs are appropriate for encoding objects of the algebra. By overriding the method to return more specific classes than Object, you make more output codecs available in those places.

Overrides:

getClassOfValues in class Algebra<List<String>>

Returns:

parseString

public List<String> parseString(String representation)

Description copied from class: Algebra

Resolves the string representation of some element of the algebra's domain to this element. For instance, the method TreeAlgebra.parseString(java.lang.String) resolves the string "f(a,b)" into a tree with three nodes.

It is the job of an algebra class to keep track of the signature of the algebra. Many algebras have a potentially infinite domain (e.g. the string algebra can be used with arbitrary alphabets), so the algebra class should keep track of the symbols that were actually used in the current run of the program. The best practice is to update the signature each time the parseString method is called. The rest of the IRTG tool code takes care to call parseString of the respective algebra to obtain objects of type E, so this ensures that the signature is always up-to-date.

Specified by:

parseString in class Algebra<List<String>>

Returns:

representAsString

public String representAsString(List<String> object)

Description copied from class: Algebra

Returns a string representation of this object. The default implementation simply calls the object's Object.toString() method. Concrete algebras may overwrite this implementation for algebra-specific string representations. Whenever Alto knows to which algebra an object belongs, it will attempt to call this method instead of the generic toString to produce algebra-specific string representations.

Overrides:

representAsString in class Algebra<List<String>>

Returns:

getSentenceLength

public static int getSentenceLength(List<String> sentence)

getMaxChartSize

public static int getMaxChartSize(int sentenceLength)

getBinaryConcatenation

public String getBinaryConcatenation()

Returns the concatenation symbol for this algebra. This is important for non-binary string algebras which extend this class.

Returns: