package nl.bluering;
import java.util.*;

public abstract class NameSpace
{
 private Hashtable h=new Hashtable();
 protected NameSpace next;

 public NameSpace(){}
 
 protected Object objectget(String s,boolean create)
 {
  Object r=h.get(s);
  if(r==null&&next!=null)
  	r=next.objectget(s,false);
  if(r==null&&create)
  	r=create(s);
  return r;	
 }
 
 /**
 * returns the variable 
 */
 
 Variable object2var(Object o,boolean create,String name)
 {
  if(o instanceof Variable)
   return (Variable)o;
  if (o instanceof Vertical) 
  {Vertical v=(Vertical) o;
   if(v.canget())
    return v.get();
   if(create)	
    return v.newlocal(new Variable(name));  
  } 
  return null;
 }
 
 public Variable getvar(String x,boolean create)
 {Object o=objectget(x,create);
  if(o==null)
   return null;
  return object2var(o,create,x);
 }
 
 protected void objectput(String s,Object o)
 {h.put(s,o);
 }
 
 abstract Object create(String s);
 
 public void dump(ExpWriter ew)
 {
   Object o;
   for (Enumeration e = h.elements() ; e.hasMoreElements() ;)
   { 
     Variable v=object2var(e.nextElement(),false,null);
	 if (v!=null)
	 {ew.write(v.toString());
      ew.write(" = ");
	  ew.write(v.getexp());
      ew.write("\n");
     }
   }
 }

}

class FlatSpace extends NameSpace
{
 public FlatSpace()
 {}
 
 Object create(String s)
 {
  Variable v=new Variable(s);
  objectput(s,v);
  return v;
 }
}


class StackSpace extends NameSpace
{
 public StackSpace()
 {}
 
 Object create(String s)
 {
  Vertical v=new Vertical(s);
  objectput(s,v);
  return v;
 }
 
 Vertical getvertical(String s,boolean create)
 {return (Vertical)objectget(s,create);
 }
 
}