package listFW.visitor;

import listFW.*;

/**
 * Counts the number of non-negative integers in the host list.
 * @author DXN
 */
public class NonNegCount implements IListAlgo {

    public Object emptyCase(IEmptyList host, Object inp) {
        return new Integer(0);
    }

    public Object nonEmptyCase(INEList host, Object inp) {
        int f = ((Integer)host.getFirst()).intValue();
        Integer rCount = (Integer)host.getRest().execute(this, null);
        if (0 <= f) {
            return new Integer(1 + rCount.intValue());
        }
        return rCount;

    }
}