Re: default formal parameters in generic declarations

["Randy Brukardt" <randy@rrsoftware.com>]

"Eric Hughes" <eric.eh9@gmail.com> wrote in message
news:a520f018-097c-406b-a3e3-387a28d38216@s8g2000prg.googlegroups.com...
> Eric Hughes <eric....@gmail.com> writes:
> > Formal
> > objects and subprograms can have default values.  Formal types and
> > packages cannot.  Could someone point me to the discussion where this
> > inconsistency was decided to be a good thing?
>
> On Mar 2, 10:42 am, Robert A Duff <bobd...@shell01.TheWorld.com>
> wrote:
> > It is not a good thing.
>
> The absence of this expression is not a good thing, but my question
> was more about the tradeoffs, not in the language itself, but in the
> whole context of the creation of the language.  Was it considered too
> late to be understood?  Were there too many prerequisites?  Was not a
> high enough priority?  _On balance_ it must have been a good thing,
> because it didn't happen.  I am assuming it was considered.

It surely was considered for the most recent language update, because I
proposed it. See AI-299. I thought it would give up more flexibility for
defining a set of containers libraries. It was not approved mainly because
of two reasons: the proposed syntax wasn't liked much, but no one had a
better idea; and because it came up at a meeting which many people consider
the low point of the Ada development -- it was mostly a lot of dubious
arguments over one feature or another, and about the only things that got
accomplished was by killing proposals. (I seriously considered quitting
after that meeting.) Presumably, at least some people didn't think it was
important enough.

The net effect is that IMHO there is no *good* reason that Ada doesn't have
such defaults (now); they just got swept up in a tide of negativity. As for
the question of why they were omitted in the first place, I can't say (I
wasn't there). I would suspect that their value wasn't completely understood
at the time; I don't recall having encountered default parameters of any
kind before seeing Ada.

                     Randy Brukardt, ARG Editor