ai.krr.propositions
Class IntEncoding

java.lang.Object
  ai.krr.propositions.IntEncoding

public class IntEncoding
extends java.lang.Object

This class can be used to encode propositional symbols as integers, which have the potential of being processed far more efficiently. A positive Literal +P will be encoded as a positive integer n, its complement -P as the negative integer -n. Thus two encoded Literals are complementary if their absolute value is the same. Note that this also means that no Literal will ever be encoded as zero.

Author:

Gerhard Wickler

Field Summary

protected NamedSymbol[]	decode
protected int[]	encInts
protected NamedSymbol[]	props arrays of symbols and encodings (hashed) and decoding:

Constructor Summary

IntEncoding(int capacity)
This constructor creates a new, empty IntEncoding that has an initial capacity for encoding up to the given number of Literals.

Method Summary

protected java.lang.Object	clone() This class does not support cloning and an exception will be thrown if this method is called.
Literal	decode(int enci) This function can be used to decode the given integer, which must have been the result of a previous encoding.
int	encode(Literal lit) This function encodes the given Literal.
int	nrEncoded() This function returns the number of Symbols currently encoded.
java.lang.String	toString() This function creates a String representation of this IntEncoding.

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

props

protected NamedSymbol[] props

arrays of symbols and encodings (hashed) and decoding:

encInts

protected int[] encInts

decode

protected NamedSymbol[] decode

Constructor Detail

IntEncoding

public IntEncoding(int capacity)

This constructor creates a new, empty IntEncoding that has an initial capacity for encoding up to the given number of Literals. If this number will be exceeded a rehashing needs to be performed.

Parameters:

capacity - the initial capacity of this IntEncoding

Method Detail

clone

protected java.lang.Object clone()
                          throws java.lang.CloneNotSupportedException

This class does not support cloning and an exception will be thrown if this method is called.

Overrides:

clone in class java.lang.Object

Returns:

nothing

Throws:

java.lang.CloneNotSupportedException - will be thrown

encode

public int encode(Literal lit)

This function encodes the given Literal. The returned integer uniquely identifies the given Literal. A positive Literal +P will be encoded as a positive integer n, its complement -P as the negative integer -n. Thus two encoded Literals are complementary if their absolute value is the same. This function never returns zero. Assuming a perfect hash-value for NamedSymbols, encodings should be computed in constant time, unless rehashing is necessary.

Parameters:

lit - the Literal to be encoded as an integer

Returns:

the integer that uniquely represents the given Literal

decode

public Literal decode(int enci)

This function can be used to decode the given integer, which must have been the result of a previous encoding. The given value must not be zero and its absolute value should be less or equal to the number of Symbols encoded here.

Parameters:

the - integer to be decoded

Returns:

a new Literal that, when encoded, results in the given integer

nrEncoded

public int nrEncoded()

This function returns the number of Symbols currently encoded. Note that the number of Literals encoded can be up to twice the returned value.

Returns:

total number of NamedSymbols in this IntEncoding

toString

public java.lang.String toString()

This function creates a String representation of this IntEncoding.

Overrides:

toString in class java.lang.Object

Returns:

an enumeration of the mapped integers