/* A first "interesting" Espresso program 
 *     by CMB  8/04
 *
 * This is a program that builds a list and prints it out.  Then it
 * modifies the list, and prints part of it again.  It does not test
 * all of the features of Espresso.
 *
 * It uses class IntList, which in turn uses class IntNode.  It's a
 * somewhat realistic program: there are only a few places where we
 * have done weird stuff to illustrate language features.
 *
 * Comments strewn throughout the program mention restrictions on Espresso
 * that aren't in Java and other language features being used.
 */

/*
 * NOTE: In Espresso all methods have return values.  Many of the
 * methods here use the convention of returning the updated object as
 * the return value.  This allows a style where method calls may be
 * strung together.  See the example of this in class IntList, method
 * buildAList
 */


// the main class is only allowed to have one method.
class ListProg {
   public static void main (String[] args) {
       IntList myList;     // no initializers allowed
       myList = new IntList();

       myList.buildAList();
       myList.printList();
       System.out.println();

       myList.insertVal(3);
       myList.insertVal(5);
       myList.printList();  // test early return on 3: should print 5 only

       // no return on main
   }
}


class IntList {
    IntNode head;

    // inserts i into front of list
    IntList insertVal(int i) {
	IntNode newNode;
	newNode = new IntNode();
	newNode.init(i);

	if (head == null) {
	    head = newNode;
	}
	else {
	    newNode.setNext(head);
	    head = newNode;
	}
	return this;    // return the updated list
    }

    // builds the list (10 20 30 . . . 90 100)
    // from back to front
    int buildAList() {
	int i;     // no initializers allowed
	i = 5;
	while (0 < i) {    // no >; no for loops

	    // add two vals in each iteration just to show 
	    // stringing together method calls
	    //   (of course, this is not the clearest way to write the code).
	    // also method calls require "." form: so need explicit "this"
	    this.insertVal(i*2*10).insertVal((i*2-1)*10);  

	    i = i - 1;      // no ++ or --
	}
	return 0;  // dummy value.  all methods have to return something
    }

    // Sometimes prints the whole list, 
    //    but stops early if it gets to a 3 in the list.
    // Why?  So we can show the short-circuit &&
    int printList() {
	
	IntNode p;

	p = head;

	while (p != null && p.getVal() != 3) {  // short-circuit &&
	    System.out.println(p.getVal());
	    p = p.getNext();
	}
	    
	return 0;
    }
}


class IntNode {
    int data;
    IntNode next;

    IntNode init(int num) {
	data = num; 
	next = null;  // same as default value: but do this for clarity
	return this;
    }

    IntNode setNext(IntNode nextVal) {
	next = nextVal;
	return this;
    }
    
    IntNode getNext() {
	return next;
    }

    int getVal() {
	return data;
    }
}