+ * This class represents a set of reference types. The set contains
+ * all types that are castable to all the bottom types by a widening
+ * cast and to which one of the top types can be casted to by a
+ * widening cast.
*
- * For a totally unknown type topType is tObject and bottomType is
- * null. It is always garanteed that topType is an Array or an Object
- * and that bottomType is null or an Array or an Object.
+ * For a totally unknown reference type bottomType is tObject and
+ * topType is tNull. The bottomType is always guaranteed to be not
+ * tNull. And all topTypes must be castable to all bottom types with
+ * a widening cast.
*
- * The hintType gives a hint which type it probably is. It is used to
- * generate the type declaration.
+ * To do intersection on range types, the reference types need three
+ * more operations: specialization, generalization and
+ * createRange.
+ * + * specialization chooses all common sub type of two types. It is + * used to find the bottom of the intersected interval.
+ * + * generalization chooses the common super type of two types. It + * is used to find the top of the intersected interval.
+ *
+ * When the new interval is created with createRangeType
+ * the bottom and top are adjusted so that they only consists of
+ * possible types. It then decides, if it needs a range type, or if
+ * the reference types already represents all types.
*
* @author Jochen Hoenicke
- * @date 98/08/06
- */
+ * @see ReferenceType
+ * @date 98/08/06 */
public class RangeType extends Type {
+ /**
+ * The bottom type set. All types in this range type can be casted
+ * to all bottom types by a widening cast.
+ */
final ReferenceType bottomType;
+ /**
+ * The top type set. For each type in this range type, there is a
+ * top type, that can be casted to this type.
+ */
final ReferenceType topType;
+
+ /**
+ * Create a new range type with the given bottom and top set.
+ */
public RangeType(ReferenceType bottomType,
ReferenceType topType) {
super(TC_RANGE);
@@ -49,53 +75,63 @@ public class RangeType extends Type {
this.topType = topType;
}
+ /**
+ * Returns the bottom type set. All types in this range type can
+ * be casted to all bottom types by a widening cast.
+ * @return the bottom type set
+ */
public ReferenceType getBottom() {
return bottomType;
}
+ /**
+ * Returns the top type set. For each type in this range type,
+ * there is a top type, that can be casted to this type.
+ * @return the top type set
+ */
public ReferenceType getTop() {
return topType;
}
+
+ /**
+ * Returns the hint type of this range type set. This returns the
+ * singleton set containing only the first top type, except if it
+ * is null and there is a unique bottom type, in which case it returns
+ * the bottom type.
+ * @return the hint type.
+ */
public Type getHint() {
return topType == tNull && bottomType.equals(bottomType.getHint())
? bottomType.getHint(): topType.getHint();
}
+ /**
+ * Returns the canonic type of this range type set. This returns the
+ * singleton set containing only the first top type.
+ * @return the canonic type.
+ */
+ public Type getCanonic() {
+ return topType.getCanonic();
+ }
+
+ /**
+ * The set of super types of this type. This is the set of
+ * super types of the top type.
+ * @return the set of super types.
+ */
public Type getSuperType() {
return topType.getSuperType();
}
+ /**
+ * The set of sub types of this type. This is the set of
+ * sub types of the bottom types.
+ * @return the set of super types.
+ */
public Type getSubType() {
- return bottomType.getSubType();
+ return tRange(bottomType, tNull);
}
-
-// /**
-// * Create the type corresponding to the range from bottomType to this.
-// * @param bottomType the start point of the range
-// * @return the range type, or tError if not possible.
-// */
-// public ReferenceType createRangeType(ReferenceType bottomType) {
-// throw new AssertError("createRangeType called on RangeType");
-// }
-
-// /**
-// * Returns the common sub type of this and type.
-// * @param type the other type.
-// * @return the common sub type.
-// */
-// public ReferenceType getSpecializedType(ReferenceType type) {
-// throw new AssertError("getSpecializedType called on RangeType");
-// }
-
-// /**
-// * Returns the common super type of this and type.
-// * @param type the other type.
-// * @return the common super type.
-// */
-// public Type getGeneralizedType(Type type) {
-// throw new AssertError("getGeneralizedType called on RangeType");
-// }
/**
* Checks if we need to cast to a middle type, before we can cast from
@@ -122,13 +158,11 @@ public class RangeType extends Type {
public String toString()
{
- if (topType == tNull)
- return "<" + bottomType + "-NULL>";
return "<" + bottomType + "-" + topType + ">";
}
public String getDefaultName() {
- throw new AssertError("getDefaultName() not called on Hint");
+ throw new AssertError("getDefaultName() called on range");
}
public int hashCode() {