import java.util.HashMap;

/**
 * Class for representing a simple variable table, mapping variables to their values.
 * 
 * @author Dave Reed
 * @version 2/9/07
 */
public class VariableTable
{
	private HashMap<String, Integer> varMap;
	
	/**
	 * Constructs an empty variable table, mapping variable names to values.
	 */
	public VariableTable() {
	    varMap = new HashMap<String, Integer>();
	}
	
	
	/**
	 * Assigns a new value to a variable in the table.
	 *   @param var the variable name to be assigned to
	 *   @param val the value to be assigned to var
	 */
	public void assign(String var, int val) {
	    varMap.put(var, val);
	}
	
	/**
	 * Looks up the value of a variable in the table, assigning that variable
	 * to be 0 if it is not already present
	 *   @param var the variable to be looked up
	 *   @return the value associated with that variable
	 */
	public int lookup(String var) {
	    if (!varMap.containsKey(var)) {
	        this.assign(var, 0);
	    }
	    return varMap.get(var);
	}
}