import schemeFW.*;

/**
 * Inserts an Integer into an ordered host list, assuming the host list contains
 * only Integer objects.
 * @author D. X. Nguyen
 */
public class InsertInOrder implements IListAlgo {

    public static final InsertInOrder Singleton = new InsertInOrder();
    private InsertInOrder() {
    }

    /**
     * This is easy, don't you think?
     * @param inp an Integer to be inserted in order into host.
     */
    public Object emptyCase(IEmptyList host, Object inp) {
        return new NEList(inp, host);
    }

    /**
     * Recur!
     * @param inp an Integer to be inserted in order into host.
     */
    public Object nonEmptyCase(INEList host, Object inp) {
        int n = ((Integer)inp).intValue();
        int f = ((Integer)host.getFirst()).intValue();
        return n < f?
                new NEList(inp, host):
                new NEList(host.getFirst(),
                                    (IList)host.getRest().execute(this, inp));
    }
}