/*  zweic -- a compiler for zwei
 *
 *  Stephane Micheloud & LAMP
 *
 *  $Id$
 */

package zweic;

// Internal type
abstract class Type {

  override def toString(): String = this match {
	case IClassType => "ClassType";
	case IIntType => "IntType"
	case INullType => "NullType"
    case IBadType => "<Bad>"
  }

  def isSubtype(that: Type): Boolean = Pair(this, that) match {
    // ... à compléter ...
    case _ => false
  }

  def isSametype(that: Type): Boolean = Pair(this, that) match {
    // ... à compléter ...
    case _ => false
  }

  def lub(that: Type): Option[Type] = Pair(this, that) match {
	case Pair(IIntType, IIntType) => IIntType
	case Pair(IClassType(x), INullType) => t1
	case Pair(INullType, IClassType(x)) => t2
	case Pair(IClassType(c1), IClassType(c2)) =>
	  intersection(c1.superclasses, c2.superclasses) match {
		case t :: ts => t
		case List() => badLub(t1, t2)
	  }
	case x => badLub(t1, t2)
  }

}

// Class type
case class IClassType(c: ClassSymbol) extends Type;

// Integer type
case object IIntType extends Type;

// Null type
case object INullType extends Type;

// Bad type
case object IBadType extends Type;