[PRL] the "success" of types

[William D Clinger]

Felix wrote:
> Would you agree that in your example, you could have written the same
> invariant down as a comment in English in Java 1.4, and that it would
> have had the same effect (or lack thereof) on the dynamic semantics?

I would agree to that were it true, and it is almost (but
not quite) true.

Greg Pettyjohn wrote:
> Emphasize "approximately". When I write a purpose statement in Scheme:
> 1. It is preceded by a ';' and thus I know it is a comment and can never
> be checked statically nor dynamically. Comments never masquerade as a
> feature of the language/type-system and in that regard can't cause
> confusion.

What I wrote was not a comment.  It is "checked" by the
Java compiler at compile time, but you have to understand
what that means.  It means very little, but it does mean
something, as can be seen by changing two lines:

        List<Integer> xint = (List<String>) x;
        List<Integer> yint = (List<String>) y;

Felix again:
> If so, would you agree that is a shift from talking about programming
> language research over to software development methodology?
> (Although maybe we've only been talking about the latter this whole
> time, and I just missed that aspect of the conversation.)

The inside joke here is that I don't have a clue what this
thread is supposed to be about.  I had a scheduling conflict
that made me miss the talk at which this came up, so all I
know is what I've read in the thread.  In particular, I do
not know Matthias's reasons for carrying on this discussion
in public; I assumed it was just random silliness.

Will