//variable node for the dynamic list - could be in a separate file
class VariableNode {
    char name;
    int value;
    VariableNode next;


    public VariableNode (char varname, int value) {
	this.name = varname;
	this.value = value;
	next = null;
    }
}


//constructor create a new list - i.e. empty linked list
public class VList {
    VariableNode head;

    public VList () {
	head = null;
    }

    //insert function
    public void insert (char name, int val) {
	
	//first go through list to
	//see if node is present
	VariableNode iterator = head;
	boolean found = false; //assume that it is not found
	
	//loop though list
	while(iterator != null) {
	    if(iterator.name == name) {
		iterator.value = val; //if you find it - reset value
		found = true;        //and set a flag to say that it was found 
		break;
	    }
	    iterator = iterator.next; //advance through the list
	}
	//If it was not in the list - make a new node
	if(!found) {
	    VariableNode temp = new VariableNode(name, val);
	    temp.next = head;
	    head = temp;

	}
    }


    //extra method not required, but nice - just checks to see
    //if the character was already there
    public boolean isPresent (char name) {
	VariableNode iterator = head;
	while (iterator != null) {
	    if (iterator.name == name)
		break;
	    iterator = iterator.next;
	}

	return (iterator == null);
    }

    //method to set new value
    public void setValue (char name, int val) {
	VariableNode iterator = head;
       	while (iterator != null) {
	    if (iterator.name == name)
		break;
	    iterator = iterator.next;
	}
	iterator.value = val;

    }



    //get value - lookup method to retrive value of a variable
    
    public int getValue (char name) {
	VariableNode iterator = head;
	
	//default return in case it is not there
	//this sets all variables not in list to 0
	int ret = 0;
	
	//loop though to find value
	//when you find it set ret to the value stored
	//if it is not found ret stays the same
	while (iterator != null) {
	    if (iterator.name == name)
		ret = iterator.value;
	    iterator = iterator.next;
	}
	return ret;
    }

    //debug function that just prints the list
    public void print () {
	VariableNode iterator = head;
	while (iterator != null) {
	    System.out.println ("variable " + iterator.name + " has value=" + iterator.value);
	    iterator = iterator.next;
	}
    }
}