/*
* 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;
import java.util.Iterator;
import java.util.NoSuchElementException;
import kodkod.util.ints.Ints;
/**
* A logic NOT gate.
*
* @invariant this.op = Operator.NOT
* @invariant #inputs = 1
* @invariant this.label = -inputs.label
* @invariant label in (-Integer.MAX_VALUE..-1]
* @author Emina Torlak
*/
public final class NotGate extends BooleanFormula {
private final int hashcode;
/**
* Constructs a new NotGate with the given formula as its input.
* @requires input != null && input !in NotGate
* @ensures this.inputs' = 0->input && this.output'.label = -input.label
*/
NotGate(BooleanFormula input) {
super(input);
this.hashcode = Ints.superFastHash(-input.label());
}
/**
* Returns a hash of this inverter's label.
* @return Ints.superFastHash(this.label)
*/
@Override
int hash(Operator op) {
return hashcode;
}
/**
* Returns an iterator that returns this gate's single input.
* @return an iterator over this.inputs.
*/
@Override
public Iterator<BooleanFormula> iterator() {
return new Iterator<BooleanFormula>() {
boolean hasNext = true;
public boolean hasNext() {
return hasNext;
}
public BooleanFormula next() {
if (!hasNext) throw new NoSuchElementException();
hasNext = false;
return negation();
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
/**
* Returns the label for this value.
* @return this.label
*/
@Override
public final int label() { return -negation().label(); }
/**
* Returns 1.
* @return 1.
*/
@Override
public int size() {
return 1;
}
/**
* Passes this value and the given
* argument value to the visitor, and returns the resulting value.
* @return the value produced by the visitor when visiting this node
* with the given argument.
*/
@Override
public <T, A> T accept(BooleanVisitor<T,A> visitor, A arg) {
return visitor.visit(this, arg);
}
/**
* Returns a string representation of this inverter.
* @return a string representation of this inverter.
*/
public String toString() {
return "!" + negation().toString();
}
/**
* Returns Operator.NOT.
* @return Operator.NOT
*/
@Override
public kodkod.engine.bool.Operator op() {
return kodkod.engine.bool.Operator.NOT;
}
/**
* Returns this.input[i].
* @return this.input[i]
* @throws IndexOutOfBoundsException i != 0
*/
@Override
public BooleanFormula input(int i) {
if (i != 0) throw new IndexOutOfBoundsException();
return negation();
}
/**
* Returns a hashcode for this inverter.
* @return a hashcode for this inverter.
*/
public int hashCode() {
return hashcode;
}
}