finiteAutomata
Class CNFRule

java.lang.Object
  finiteAutomata.CNFRule

public class CNFRule
extends java.lang.Object

Rules for the CNF class.

There are three types of rules allowed in a CNF grammar. Type 0 rules transform a variable to a pair of variables; type 1 rules transform a variable to a terminal symbol; and type 2 rules transform the start variable to the empty string (epsilon). The CNFRule class is used to represent rules of types 0 and 1.

Data Fields: A CNFRule has a "type" (integer code 0 or 1), three integer variables "var1", "var2", "var3", and a char variable "term" (terminal symbol).

Type 0 rules are form vn -> vi vj where i and j are non-zero. In this case, type = 0, var1 = n, var2 = i, var3 = j, and "term" is irrelevant.

Type 1 rules are form vn -> t. In this case, type = 1, var1 = n, term = t, and "var2", "var3" are irrelevant.

Version:

Fall 2007

Author:

Barbara Wahl

Field Summary

protected char	term right-hand-side terminal symbol (for type 1)
protected int	type indicates type 0 or type 1
protected int	var1 left-hand-side variable
protected int	var2 first right-hand-side variable (for type 0)
protected int	var3 second right-hand-side variable (for type 0)

Constructor Summary

CNFRule(CNFRule current)
Copy constructor.

CNFRule(int n, char t)
2-parameter constructor for type 1 rule, "vn -> t".

CNFRule(int n, int i, int j)
3-parameter constructor for type 0 rule, "vn -> vi vj".

Method Summary

boolean	equals(java.lang.Object other) Tests whether this CNFRule and the given CNFRule are logically equal.
static void	main(java.lang.String[] args)
char	term() Returns term, the terminal symbol on RHS (or '-' if type 0).
java.lang.String	toString() Returns a pretty String representation of this rule.
int	type() Returns the type.
int	var1() Returns var1, the LHS variable.
int	var2() Returns var2, the first RHS variable (or '-' if type 1).
int	var3() Returns var3, the second RHS variable (or '-' if type 1).

Methods inherited from class java.lang.Object

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

Field Detail

type

protected int type

indicates type 0 or type 1

var1

protected int var1

left-hand-side variable

var2

protected int var2

first right-hand-side variable (for type 0)

var3

protected int var3

second right-hand-side variable (for type 0)

term

protected char term

right-hand-side terminal symbol (for type 1)

Constructor Detail

CNFRule

public CNFRule(int n,
               int i,
               int j)

3-parameter constructor for type 0 rule, "vn -> vi vj".

Parameters:

n - LHS variable

i - first RHS variable

j - second RHS variable

Precondition:

n >= 0, i > 0, j > 0

Postcondition:

creates the type 0 CNFRule for "vn -> vi vj" (term = '-')

CNFRule

public CNFRule(int n,
               char t)

2-parameter constructor for type 1 rule, "vn -> t".

Parameters:

n - LHS variable

t - terminal symbol

Precondition:

n >= 0

Postcondition:

creates the type 1 CNFRule for "vn -> t" (var2 = var3 = -1)

CNFRule

public CNFRule(CNFRule current)

Copy constructor.

Parameters:

current - CNFRule to be copied

Precondition:

current is not null

Postcondition:

constructs a new CNFRule with same attributes as current

Method Detail

type

public int type()

Returns the type.

Returns:

int type

var1

public int var1()

Returns var1, the LHS variable.

Returns:

int var1

var2

public int var2()

Returns var2, the first RHS variable (or '-' if type 1).

Returns:

int var2

var3

public int var3()

Returns var3, the second RHS variable (or '-' if type 1).

Returns:

int var3

term

public char term()

Returns term, the terminal symbol on RHS (or '-' if type 0).

Returns:

char term

toString

public java.lang.String toString()

Returns a pretty String representation of this rule.

Overrides:

toString in class java.lang.Object

Returns:

String for pretty-printing the rule

equals

public boolean equals(java.lang.Object other)

Tests whether this CNFRule and the given CNFRule are logically equal.

Overrides:

equals in class java.lang.Object

Parameters:

other - CNFRule to compare with this

Returns:

true iff the two rules are logically equivalent

Precondition:

other is a non-null CNFRule object

main

public static void main(java.lang.String[] args)