package listFW.visitor;

import listFW.*;

/**
 * Accepts as input the accumulated sum of the list preceding the host and
 * adds the sum of the host to the accumulated sum.
 * @author DXN
 */
public class HelpGetSum implements IListAlgo {

    /**
     * @param inp Integer the accumulated sum of the list preceding host.
     * @return Integer inp - we are done!
     */
    public Object emptyCase(IEmptyList host, Object inp) {
        return inp;
    }

    /**
     * Adds the host's first to inp and recurs by passing the resulting sum to
     * the rest.
     * @param inp Integer the accumulated sum of the list preceding host.
     * @return Integer
     */
    public Object nonEmptyCase(INEList host, Object inp) {
        int f = ((Integer)host.getFirst()).intValue();
        int acc = ((Integer)inp).intValue();
        return host.getRest().execute(this, new Integer(f + acc));
    }
}