/*
* Kodkod -- Copyright (c) 2005-present, Emina Torlak
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package kodkod.engine.bool;
/**
* Represents a boolean value, which may be a {@link kodkod.engine.bool.BooleanFormula formula}
* or a {@link kodkod.engine.bool.BooleanConstant constant}. Boolean formulas are produced by
* {@link kodkod.engine.bool.BooleanFactory circuit factories}. Each value is associated with
* an integer label; the labels are unique within a given factory.
* A boolean value with a negative label -|l| represents the negation of the value with the positive
* label |l|. Non-constant values are not shared among factories.
*
* @specfield op: Operator
* @specfield label: [-Integer.MAX_VALUE, Integer.MAX_VALUE]
* @invariant no c: BooleanValue - this | some components.c & components.this && c.label = this.label
* @author Emina Torlak
*/
public abstract class BooleanValue implements Comparable<BooleanValue> {
BooleanValue() {}
/**
* Returns the negation of this boolean value
* @return { f: BooleanFormula | [[f]] = ![[this]] }
*/
abstract BooleanValue negation();
/**
* Returns the label for this value.
* @return this.label
*/
public abstract int label();
/**
* Returns the operator representing the function
* computed by this gate.
* @return this.op
*/
public abstract Operator op();
/**
* Boolean components are ordered according to their labels.
* Note that the ordering is well defined on components produced by the same factory.
* Specifically, this comparison function is consistent with equals for the components
* produced by the same factory, but may not be for the components produced by different factories.
* @return 0 if the label of this and other are the same, a negative
* integer if the label of this is smaller than the label of other; and
* a positive integer otherwise.
*/
public final int compareTo(BooleanValue other) {
return label() - other.label();
}
}