// FILE. . . . . d:/hak/hlt/src/hlt/math/matrix/sources/PredsIterator.java
// EDIT BY . . . Hassan Ait-Kaci
// ON MACHINE. . Hak-Laptop
// STARTED ON. . Fri Nov 29 00:07:28 2019
/**
* @version Last modified on Fri Nov 29 11:23:08 2019 by hak
* @author Hassan Aït-Kaci
* @copyright © by the author
*/
package hlt.math.matrix;
import hlt.language.util.IntIterator;
/**
* This is a class implementing the hlt.language.util.IntIterator
* interface for iterating through the left nodes that are the
* predecessors of a given right node in a BipartiteGraph.
*
* @see BipartiteGraph
* @see SuccsIterator
*/
public class PredsIterator implements IntIterator
{
/**
* The BipartiteGraph concerned by this
* PredsIterator.
*/
private BipartiteGraph graph;
/**
* The right node index concerned by this PredsIterator.
*/
private int right;
/**
* The number of left nodes
*/
private int lefts;
/**
* The index of the first left node successor of right in
* graph, or -1 if there is none.
*/
private int first;
/**
* The index of the last left node successor of right in
* graph, or -1 if there is none.
*/
private int last;
/**
* Current left node index in this PredsIterator.
*/
private int index;
/**
* Construct a PredsIterator for right in the given
* graph.
*/
public PredsIterator (BipartiteGraph graph, int right)
{
this.graph = graph;
this.right = right;
lefts = graph.order();
first = graph.firstPredecessor(right); // -1 if no predecessors
last = graph.lastPredecessor(right); // -1 if no predecessors
index = first;
}
/**
* Return true iff this PredsIterator has more
* indices remaining.
*/
public final boolean hasNext ()
{
if (index > last)
return false;
while (index <= last && !graph.isEdge(index,right))
index++;
return index <= last; // NB: if right has no predecessors, this returns false (since last = -1)
}
/**
* Return the index of the first successor of right, or
* -1 if none exists.
*/
public final int first ()
{
return first;
}
/**
* Return the index of the last successor of right, or
* -1 if none exists.
*/
public final int last ()
{
return last;
}
/**
* Return the next successor node index in this
* PredsIterator, or -1 if there is none
* remaining.
*/
public final int next ()
{
return index == lefts ? -1 : index++;
}
}