Re: Q: access to subprogram

[dewar@cs.nyu.edu (Robert Dewar)]

iJon said

"As several have pointed out, this is not particularly convincing.  The
best evidence indicates that this was a red-herring in this instance."

Nope, this was not a red herring, it (the concern about backend 
reimplementation) was the major focus of the argument. Remember that
this feature was being discussed very late on. Jon, did you read
all the references that Norman pointed to, they will give you a
clear picture of the discussion on this issue.

The reason it was discussed late on was Bill Taylor's late plea to
reexamine this issue in light of the iterator issue (well worth
reading, it is the first of Norman's references). This got a lot
of people interested again, and in the absence of implementatoin
concerns, it is clear that the design would have been revisited.

This late discussion was entirely focused on the issue of

  importance of this functionality

      vs

  impact on existing backends

Note that, as I have tried to emphasize before, static links vs displays
was an irrelevant issue then and now. I suppose someone could ake
the position of the original Steelman and worry about the impact on
implementations at a conceptual level, but in fact NO ONE took this
position that I can remember. The issue was very much focused on the
fact that at least two existing Ada technologies depended on displays
(you should also carefully look at Randy's concerns about shared
generics -- as always Randy was the one defending the shared generic
approach, and there are some interesting concerns here).

Tuck is certainly right that the reason that this originally disappeared
was in the general mood of simplification, although some would feel that
the restriction here is not a simplification but rather an instance of
introducing arbitrary restrictions that make things more complex.

But the failure of Bill Taylor's arguments with repsect to iterators
to succeed in getting the feature in was definitely the above consideration,
and as I say, you should read all the articles -- of course the articles
only capture a part of the argument -- you should also read Jim's
excellent minutes of the Villar's meeting where this issue was discussed
and finally decided on.