Re: Still no typedef

Daniel Pitts <>
Thu, 06 Dec 2007 11:56:44 -0800
Andreas Leitgeb wrote:

Daniel Pitts <> wrote:

Patricia Shanahan wrote:

Here's an alternative syntax suggestion:
class FooInt Foo<Comparator<Integer>>;

I think I would prefer interface over class for this.

No, not really, afterall one should also be able to do
 FooInt x=new FooInt(42);
lateron. IMHO, at least.

Right, but FooInt is an interface to the class Foo<Comparator<Integer>>.

All that it *really* means is FooInt is an alias for
Foo<Comparator<Integer>>. Perhaps calling it a Type Alias is better
than a TypeDef.

Now that I think more about it, type aliases are another form of
abstraction/indirection that might be useful, especially if they are
implemented as more than typedefs in c++...

Imaging this:

class MyClass {
   /* The following says,
      ListType is the specific type we need,
      and is assignable to List<FooBar>.
      The fact that it is ArrayList is "hidden" from clients.
      I'm assuming types would be static members automatically,
      but if there were a way to have instance-specific types,
      that would be even more "interesting".
   public type ListType implements List<FooBar> = ArrayList<FooBar>();
   private ListType list;
   public void setBackingList(ListType list) {
     this.list = list;

   public ListType getList() {
      return list;

class OtherClass {
   public void things() {
     MyClass mc = new MyClass();
     mc.setBackingList(new MyClass.ListType());
     MyClass.ListType lt = mc.getList();
     // lt's compile time type is List<FooBar> & MyClass.ListType.
MyClass.ListType doesn't expose ArrayList methods.}

This allows for a kind of interface that you can instantiate. Don't
mind me, random babbling and stream-of-consciousness dump.

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