lp.struct
Class LpLiteral

java.lang.Object
  lp.struct.LpAbstractStructureUnit
      lp.struct.LpLiteral

All Implemented Interfaces:

LpStructureUnit

public class LpLiteral
extends LpAbstractStructureUnit

This class represents a literal in logic programming. Such a literal can be positive or negative (default) and relates to exactly one atom represented by a instance.

Version:

1.0.0

Author:

Martin Slota

See Also:

LpAtom, LpRule

Field Summary

private LpAtom	atom The atom part of this literal.
private boolean	positive The polarity of this literal.

Fields inherited from class lp.struct.LpAbstractStructureUnit

TO_STRING_BUFFER

Constructor Summary

LpLiteral(boolean positive, LpAtom atom)
Creates a new instance with the given values as members.

Method Summary

void	accept(LpStructureUnitVisitor visitor) Accepts LpStructureUnitVisitor instance, i.e. calls its visitor.visit(this).
boolean	equals(Object obj) Returns true if and only if obj is a LpLiteral instance, it has the same polarity as this literal, its underlying LpAtom instance is equal to this literal's underlying LpAtom instance
List<LpTerm>	getArguments() Returns the list of arguments of this literal.
LpAtom	getAtom() Returns the atom used to create this literal, the same that was given to the constructor.
LpPredicate	getPredicate() Returns the predicate symbol of this literal.
int	hashCode() Overriden in order to maintain the general contract of Object.hashCode().
boolean	isPositive() Returns true if this literal is positive and false otherwise.

Methods inherited from class lp.struct.LpAbstractStructureUnit

toString, toUnmodifiableList, toUnmodifiableSet

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

positive

private final boolean positive

The polarity of this literal. true if this is a positive literal, false if this is a default literal.

atom

private final LpAtom atom

The atom part of this literal.

Constructor Detail

LpLiteral

LpLiteral(boolean positive,
          LpAtom atom)

Creates a new instance with the given values as members. Should only be directly used by methods of LpAtom.

Parameters:

positive - true if it's supposed to be a positive literal, false if it's supposed to be a default literal

atom - the atom part of this literal

Throws:

IllegalArgumentException - if atom is null

Method Detail

isPositive

public boolean isPositive()

Returns true if this literal is positive and false otherwise.

Returns:

true iff this literal is positive

getAtom

public LpAtom getAtom()

Returns the atom used to create this literal, the same that was given to the constructor.

Returns:

the LpAtom instance given in the constructor

getPredicate

public LpPredicate getPredicate()

Returns the predicate symbol of this literal.

Returns:

the LpPredicate instance representing the predicate symbol used in this literal

See Also:

LpAtom.getPredicate()

getArguments

public List<LpTerm> getArguments()

Returns the list of arguments of this literal.

Returns:

an unmodifiable view of the argument list of this literal

See Also:

LpAtom.getArguments()

accept

public void accept(LpStructureUnitVisitor visitor)

Accepts LpStructureUnitVisitor instance, i.e. calls its visitor.visit(this).

Parameters:

visitor - the visitor to accept

equals

public boolean equals(Object obj)

Returns true if and only if

1. obj is a LpLiteral instance,
2. it has the same polarity as this literal,
3. its underlying LpAtom instance is equal to this literal's underlying LpAtom instance

Overrides:

equals in class Object

Parameters:

obj - the object to compare with

Returns:

true if this object is equal to obj according to the description above, and false otherwise

See Also:

LpAtom.equals(Object)

hashCode

public int hashCode()

Overriden in order to maintain the general contract of Object.hashCode().

Overrides:

hashCode in class Object

Returns:

the hash of this object

See Also:

LpAtom.hashCode()