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/*
* esodata - data structures and other things, of varying utility
* Copyright 2022, Ben Culkin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package bjc.data;
import java.util.Iterator;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;
/**
* An iterator that generates a series of elements from a single element.
*
* @author bjculkin
*
* @param <E>
* The type of element generated.
*/
public class GeneratingIterator<E> implements Iterator<E> {
/* Our current state. */
private E state;
/* The function to use to transition states. */
private UnaryOperator<E> transtion;
/* The predicate to indicate where to stop. */
private Predicate<E> stpper;
/**
* Create a new generative iterator.
*
* @param initial
* The initial state of the generator.
*
* @param transition
* The function to apply to the state.
*
* @param stopper
* The predicate applied to the current state to determine
* when to stop.
*/
public GeneratingIterator(E initial, UnaryOperator<E> transition,
Predicate<E> stopper) {
state = initial;
transtion = transition;
stpper = stopper;
}
@Override
public boolean hasNext() {
return !stpper.test(state);
}
/*
* @NOTE
*
* As this currently is, it only works correctly assuming that next() is only
* called when hasNext() is true. Should we safeguard against people who are not
* doing the right thing?
*/
@Override
public E next() {
state = transtion.apply(state);
return state;
}
/**
* Sets the state of this iterator.
*
* @param newState The new state value.
*
* @return The old state value.
*/
public E setState(E newState) {
E oldState = this.state;
this.state = newState;
return oldState;
}
}
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