lp.struct
Class LpRule

java.lang.Object
  lp.struct.LpAbstractStructureUnit
      lp.struct.LpRule

All Implemented Interfaces:

LpStructureUnit, LpTerm

public class LpRule
extends LpAbstractStructureUnit
implements LpTerm

Represents a logic programming rule. Each rule has a literal (represented by a LpLiteral instance) called its head and a set of such literals (also represented by LpLiteral instances) called its body. A rule can have null as its head (in that case it is an integrity constraint) and it can have null as its body (in that case it is a fact).

Version:

1.0.0

Author:

Martin Slota

Field Summary

private Set<LpLiteral>	body The rule's body.
private LpLiteral	head The rule's head.

Fields inherited from class lp.struct.LpAbstractStructureUnit

TO_STRING_BUFFER

Constructor Summary

LpRule(LpLiteral ruleHead, Set<LpLiteral> ruleBody)
Creates a new instance of LpRule with the given ruleHead and ruleBody.

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 LpRule instance, its head is equal to this rule's head, i.e. either they are both null or they are equal according to LpLiteral.equals(Object), its body is equal to this rule's body, i.e. either they are both null or one is null and the other has Set.size() equal to 0 or they are equal according to Set.equals(Object).
Set<LpLiteral>	getBody() Returns the list literals in the body of this rule.
int	getBodySize() Returns the number of literals in this rule's body.
LpLiteral	getHead() Returns the head of this rule, the same that was given to the constructor.
int	hashCode() Overriden in order to maintain the general contract of Object.hashCode().

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

head

private final LpLiteral head

The rule's head.

body

private final Set<LpLiteral> body

The rule's body.

Constructor Detail

LpRule

public LpRule(LpLiteral ruleHead,
              Set<LpLiteral> ruleBody)

Creates a new instance of LpRule with the given ruleHead and ruleBody. Both ruleHead and ruleBody can have a null value, but not at the same time. Arguments of the constructor are not copied (especially the ruleBody Set). This class is immutable as long as ruleBody is not changed after creating an instance.

Parameters:

ruleHead - ruleHead of the new rule

ruleBody - ruleBody of the new rule

Throws:

IllegalArgumentException - if both ruleHead and ruleBody are null

Method Detail

getHead

public LpLiteral getHead()

Returns the head of this rule, the same that was given to the constructor.

Returns:

the LpLiteral given in the constructor as the head of this rule

getBody

public Set<LpLiteral> getBody()

Returns the list literals in the body of this rule.

Returns:

an unmodifiable version of the list of body literals from the constructor

getBodySize

public int getBodySize()

Returns the number of literals in this rule's body.

Returns:

as specified above

accept

public void accept(LpStructureUnitVisitor visitor)

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

Specified by:

accept in interface LpStructureUnit

Parameters:

visitor - the visitor to accept

equals

public boolean equals(Object obj)

Returns true if and only if

1. obj is a LpRule instance,
2. its head is equal to this rule's head, i.e. either they are both null or they are equal according to LpLiteral.equals(Object),
3. its body is equal to this rule's body, i.e. either they are both null or one is null and the other has Set.size() equal to 0 or they are equal according to Set.equals(Object).

Specified by:

equals in interface LpTerm

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:

LpLiteral.equals(Object), Set.equals(Object)

hashCode

public int hashCode()

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

Specified by:

hashCode in interface LpTerm

Overrides:

hashCode in class Object

Returns:

the hash of this object

See Also:

LpLiteral.hashCode(), Set.hashCode()