de.unidu.is.pdatalog.ds
Class Literal

java.lang.Object
  de.unidu.is.pdatalog.ds.Literal

public class Literal

extends java.lang.Object

The representation of an datalog literal. An literal is a string [!]p(t1,...,tn) where is p is a predicate name, the tis are the arguments (variable names or constants, where constants are conclosed on '') and n is the arity of the predicate. It is also called the arity of the literal. A literal can be positive (missing !) or negative (with starting !).

This class is used by Rule for storing the head literal.

Since:

2002-12-02 (predecessor 2000-07-27)

Version:

$Revision: 1.6 $, $Date: 2005/03/14 17:33:14 $

Author:

Henrik Nottelmann

Field Summary

protected Expression[]	arguments The arguments.
protected boolean	positive Being true iff this Literal is positive.
protected java.lang.String	predicateName The name of the predicate.

Constructor Summary

Literal(Literal literal)
Creates a new literal.

Literal(java.lang.String predicateName, Expression[] arguments, boolean positive)
Creates a new literal.

Literal(java.lang.String predicateName, java.util.List arguments, boolean positive)
Creates a new literal.

Method Summary

Literal	createLiteral() Creates a positive copy of this literal.
Literal	createLiteral(boolean positive) Creates a copy of this literal.
boolean	equals(java.lang.Object o) Compares the specified Object with this literal for equality.
java.util.Set	getAllArguments() Returns a set containing all arguments (variables and constants).
Expression	getArgument(int index) Returns the argument at the specified index.
java.lang.String	getArguments() Returns the arguments as a comma separated string.
int	getArity() Returns the arity of this literal.
java.util.Set	getConstants() Returns a set containing all constants (no variables).
java.lang.String	getPredicateName() Returns the predicate name.
java.util.Set	getVariables() Returns a set containing all variables (no constants).
int	hashCode() Returns the hash code value for this literal.
boolean	isPositive() Returns if this literal is positive.
boolean	isVariable(int index) Returns whether the argument at the specified index is a variable name or a constant.
void	negate() Negates this literal.
void	putAllArguments(java.util.Set set) Puts all arguments (variables and constants) into the specified set.
void	putConstants(java.util.Set set) Puts all constants (no variables) into the specified set.
void	putVariables(java.util.Set set) Puts all variables (no constants) into the specified set.
void	setArgument(int index, Expression value) Sets the argument at the specified index.
void	setNegative() Makes this literal negative.
void	setPositive() Makes this literal positive.
void	setPositive(boolean positive) Sets if this literal is positive.
void	setPredicateName(java.lang.String predicateName) Sets the predicate name.
protected java.lang.String	toHashCodeString() Returns a string representation of this literal, used for equals(Object) and hashCode().
java.lang.String	toString() Returns a datalog representation of this literal.

Methods inherited from class java.lang.Object

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

Field Detail

predicateName

protected java.lang.String predicateName

The name of the predicate.

arguments

protected Expression[] arguments

The arguments.

positive

protected boolean positive

Being true iff this Literal is positive.

Constructor Detail

Literal

public Literal(java.lang.String predicateName,
               Expression[] arguments,
               boolean positive)

Creates a new literal.

Parameters:

predicateName - predicate name

arguments - arguments (variable names or constants)

positive - true iff this literal is positive

Literal

public Literal(java.lang.String predicateName,
               java.util.List arguments,
               boolean positive)

Creates a new literal.

Parameters:

predicateName - predicate name

arguments - list of arguments (variable names or constants)

positive - true iff this literal is positive

Literal

public Literal(Literal literal)

Creates a new literal.

Parameters:

literal - to be copied

Method Detail

getPredicateName

public java.lang.String getPredicateName()

Returns the predicate name.

Returns:

predicate name

setPredicateName

public void setPredicateName(java.lang.String predicateName)

Sets the predicate name.

Parameters:

predicateName - predicate name

getArity

public int getArity()

Returns the arity of this literal.

Returns:

arity

getArguments

public java.lang.String getArguments()

Returns the arguments as a comma separated string.

Returns:

arguments

getArgument

public Expression getArgument(int index)

Returns the argument at the specified index.

Parameters:

index - index

Returns:

argument at the specified index

isVariable

public boolean isVariable(int index)

Returns whether the argument at the specified index is a variable name or a constant.

Parameters:

index - index

Returns:

flag indicating whether the argument at the specified index is a variable name or a constant

setArgument

public void setArgument(int index,
                        Expression value)

Sets the argument at the specified index.

Parameters:

index - specified index

value - new argument at the specified index

putVariables

public void putVariables(java.util.Set set)

Puts all variables (no constants) into the specified set.

Parameters:

set - destination set for all variables

putConstants

public void putConstants(java.util.Set set)

Puts all constants (no variables) into the specified set.

Parameters:

set - destination set for all constants

putAllArguments

public void putAllArguments(java.util.Set set)

Puts all arguments (variables and constants) into the specified set.

Parameters:

set - destination set for all arguments

getVariables

public java.util.Set getVariables()

Returns a set containing all variables (no constants).

Returns:

set containing all variables (no constants)

getConstants

public java.util.Set getConstants()

Returns a set containing all constants (no variables).

Returns:

set containing all constants (no variables)

getAllArguments

public java.util.Set getAllArguments()

Returns a set containing all arguments (variables and constants).

Returns:

set containing all arguments

isPositive

public boolean isPositive()

Returns if this literal is positive.

Returns:

true if this literal is positve

setPositive

public void setPositive(boolean positive)

Sets if this literal is positive.

Parameters:

positive - flag indicating if this literal is positive or negative

setPositive

public void setPositive()

Makes this literal positive. This is equivalent to setPositive(true).

setNegative

public void setNegative()

Makes this literal negative. This is equivalent to setPositive(false).

negate

public void negate()

Negates this literal.

createLiteral

public Literal createLiteral()

Creates a positive copy of this literal.

Returns:

positive copy of this literal

createLiteral

public Literal createLiteral(boolean positive)

Creates a copy of this literal.

Parameters:

positive - indicating whether the copy is positive or negative

Returns:

positive copy of this literal

toString

public java.lang.String toString()

Returns a datalog representation of this literal.

Returns:

a datalog representation of this literal

toHashCodeString

protected java.lang.String toHashCodeString()

Returns a string representation of this literal, used for equals(Object) and hashCode().

Returns:

a string representation of this literal

hashCode

public int hashCode()

Returns the hash code value for this literal. The hash code is calculated based on toHashCodeString().

Returns:

the hash code value for this literal

equals

public boolean equals(java.lang.Object o)

Compares the specified Object with this literal for equality. The comparasion is performed based on the equality of toHashCodeString().

Parameters:

o - the Object to be compared for equality with this literal

Returns:

true if the specified Object is equal to this literal