sjm.engine
Class Comparison

java.lang.Object
  |
  +--sjm.engine.Structure
        |
        +--sjm.engine.Gateway
              |
              +--sjm.engine.Comparison

public class Comparison

extends Gateway

implements BooleanTerm

A Comparison object applies a comparison operator to its terms in order to prove itself.

The functor of a comparison must be one of the strings, "<", ">", "<=", ">=", "=", or "!=", indicating comparison this object will perform during a proof. Any other functor will cause the comparison to always be false.

Here is an example of a comparison:

     Atom alpha = new Atom("alpha");
     Atom beta = new Atom("beta");
     Comparison c = new Comparison("<=", alpha, beta);
     System.out.println(c + ", " + c.canFindNextProof());
 

This prints out:

     <=(alpha, beta), true
 

Fields inherited from class sjm.engine.Gateway

open

Fields inherited from class sjm.engine.Structure

emptyList, functor, terms

Constructor Summary

Comparison(java.lang.String operator, ComparisonTerm term0, ComparisonTerm term1)
Create a comparison with the specified operator and comparison terms.

Method Summary

boolean	canProveOnce() Returns true if the comparison operator holds true between the values of this comparison's terms.
protected boolean	compare(java.lang.Object obj0, java.lang.Object obj1) Returns the result of comparing two objects, using the indicated comparison operator.
protected boolean	compareNumber(java.lang.Number n0, java.lang.Number n1) Returns the result of comparing two Numbers, using the indicated comparison operator.
protected boolean	compareString(java.lang.String s0, java.lang.String s1) Returns the result of comparing two Strings, using the indicated comparison operator.
Term	copyForProof(AxiomSource ignored, Scope scope) Create a copy that uses the provided scope.
java.lang.Object	eval() Returns Boolean.TRUE if the comparison operator holds true between the values of the two terms.

Methods inherited from class sjm.engine.Gateway

canFindNextProof, cleanup

Methods inherited from class sjm.engine.Structure

arity, equals, functorAndArityEquals, headAndTail, isList, list, list, list, listTailString, listTermsToString, terms, toString, unify, unify, unify, variables

Methods inherited from class java.lang.Object

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

Constructor Detail

Comparison

public Comparison(java.lang.String operator,
                  ComparisonTerm term0,
                  ComparisonTerm term1)

Create a comparison with the specified operator and comparison terms.

Parameters:

String - the comparison operator

ComparisonTerm - the first term

ComparisonTerm - the second term

Method Detail

canProveOnce

public boolean canProveOnce()

Returns true if the comparison operator holds true between the values of this comparison's terms.

Overrides:

canProveOnce in class Gateway

Returns:

true if the comparison operator holds true between the values of this comparison's terms.

compare

protected boolean compare(java.lang.Object obj0,
                          java.lang.Object obj1)

Returns the result of comparing two objects, using the indicated comparison operator.

Parameters:

Object - a string or number to compare

Object - a string or number to compare

Returns:

the result of comparing two objects

compareNumber

protected boolean compareNumber(java.lang.Number n0,
                                java.lang.Number n1)

Returns the result of comparing two Numbers, using the indicated comparison operator.

Parameters:

Number - a Number to compare

Number - a Number to compare

Returns:

the result of comparing the two numbers

compareString

protected boolean compareString(java.lang.String s0,
                                java.lang.String s1)

Returns the result of comparing two Strings, using the indicated comparison operator.

Parameters:

String - a String to compare

String - a String to compare

Returns:

the result of comparing the two strings

copyForProof

public Term copyForProof(AxiomSource ignored,
                         Scope scope)

Create a copy that uses the provided scope.

Overrides:

copyForProof in class Structure

Parameters:

AxiomSource - ignored

Scope - the scope to use for variables in the copy

Returns:

a copy that uses the provided scope

eval

public java.lang.Object eval()

Returns Boolean.TRUE if the comparison operator holds true between the values of the two terms.

Overrides:

eval in class Structure

Returns:

Boolean.TRUE if the comparison operator holds true between the values of the two terms.