de.uni_tuebingen.sfb.lichtenstein.formulas
Class FirstOrderEquality

java.lang.Object
  de.uni_tuebingen.sfb.lichtenstein.formulas.FormulaImpl
      de.uni_tuebingen.sfb.lichtenstein.formulas.AtomicFormula
          de.uni_tuebingen.sfb.lichtenstein.formulas.FirstOrderEquality

All Implemented Interfaces:

Formula, Visitable, Serializable

public class FirstOrderEquality
extends AtomicFormula

A class representing the atomic formula that says two first order variables are equal.

Author:

Hendrik Maryns

See Also:

Serialized Form

Constructor Summary

FirstOrderEquality(FirstOrderVariable first, FirstOrderVariable second)
Initialize a new first order equality, involving two first order variables.

Method Summary

void	accept(FormulaVisitor visitor) Accept a formula visitor.
boolean	containsVariable(Variable var) Returns whether this formula contains the given variable.
boolean	equals(Object other) Indicates whether some other object is "equal to" this one.
int	getFirstIndexOf(Variable var) Get the first index at which the given variable occurs.
FirstOrderVariable	getFirstVariable() Returns the first variable.
int	getNbVariables() Returns the number of variables in this formula.
Set<Predicate>	getPredicates() Return all predicates in this formula.
FirstOrderVariable	getSecondVariable() Returns the second variable.
Variable	getVariableAt(int index) Get the indexth variable (free or bound).
int	hashCode() Returns a hash code value for the object.
String	toString() Returns a string representation of the object.

Methods inherited from class de.uni_tuebingen.sfb.lichtenstein.formulas.AtomicFormula

getNbBoundVariables, getNbFreeVariables, getNormalForm, isFreeVariable

Methods inherited from class de.uni_tuebingen.sfb.lichtenstein.formulas.FormulaImpl

and, exists, exists, forAll, forAll, getFreeVariables, getVariables, iff, implies, isClosed, not, or

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

FirstOrderEquality

public FirstOrderEquality(FirstOrderVariable first,
                          FirstOrderVariable second)

Initialize a new first order equality, involving two first order variables.

Parameters:

first - The first variable.

second - The second variable.

Precondition:

Both variables have to be effective.

| first != null && second != null

Postcondition:

The first variable is given to the first given variable.

| new.getFirstVariable() == first

Postcondition:

The second variable is given to the second given variable.

| new.getSecondVariable() == second

Method Detail

getFirstVariable

public FirstOrderVariable getFirstVariable()

Returns the first variable.

Returns:

This is the first first order variable.

| result == getVariableAt(0)

getSecondVariable

public FirstOrderVariable getSecondVariable()

Returns the second variable.

Returns:

This is the second first order variable.

| result == getVariableAt(1)

getNbVariables

public int getNbVariables()

Returns the number of variables in this formula.

Returns:

Always 2.

| result == 2

getFirstIndexOf

public int getFirstIndexOf(Variable var)

Get the first index at which the given variable occurs.

Parameters:

var - The variable of which the index is wanted.

getVariableAt

public Variable getVariableAt(int index)
                       throws IndexOutOfBoundsException

Get the indexth variable (free or bound).

Parameters:

index - The index of the wanted variable

containsVariable

public boolean containsVariable(Variable var)

Returns whether this formula contains the given variable.

Parameters:

var - The variable to check.

getPredicates

public Set<Predicate> getPredicates()

Return all predicates in this formula.

Returns:

A first order equality cannot contain predicates.

| result.isEmpty()

equals

public boolean equals(Object other)

Indicates whether some other object is "equal to" this one.

Overrides:

equals in class FormulaImpl

Returns:

Two equalities are equal if they compare the same variables.

| let otherEquals = (FirstOrderEquality)
         other in
| if ( otherEquals.getFirstVariable() != getFirstVariable() ) | then result == false | else if (
         otherEquals.getSecondVariable() != getSecondVariable() )
| then result == false | else result == true

hashCode

public int hashCode()

Returns a hash code value for the object.

Specified by:

hashCode in class FormulaImpl

Returns:

The hash code is based on the hash codes of the variables and of the characteristic symbol.

| result ==
         getFirstVariable().hashCode() + "=".hashCode() + getSecondVariable().hashCode()

toString

public String toString()

Returns a string representation of the object.

Specified by:

toString in class FormulaImpl

Returns:

The string representations of the variables are given, with the equal sign: = in between them.

| result ==
         getFirstVariable().toString() + "=" + getSecondVariable().toString()

accept

public void accept(FormulaVisitor visitor)
            throws de.uni_tuebingen.sfb.lichtenstein.exceptions.VisitorException

Accept a formula visitor. The iteration is done by the visitor, not by the composed formulas.

Specified by:

accept in interface Visitable

Overrides:

accept in class FormulaImpl

Parameters:

visitor - The visitor that is to be accepted to do its work.

Throws:

VisitorException

A visitor can throw an exception.