Re: Ada generics

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 26 Dec 2006 08:23:32 -0800, Hyman Rosen wrote:

> Dmitry A. Kazakov wrote:
>> When you compare values of potentially different objects instead, then
>> the semantics of the comparison is not necessarily identity. In fact, it is
>> outside the language.
> 
> I think the issue here is not unlike that faced by programming
> languages when dealing with Unicode in identifiers. (I took a quick
> glance through AI-285.) There are potentially several ways that a
> character can be written in the source text, and the compilers must
> decide what it is that is written, and which forms must be considered
> identical and which distinct.

I didn't look at the AI, but it is definitely a different problem. The
language should be defined in terms of code points. The encoding of is
irrelevant. When some sequences of code points (=words) are considered
equivalent in the language like | and ! are in Ada, that is not yet
matching by structure. It were if Ada would be defined in terms of glyphs.
Fortunately it is not.

> There is certainly no problem in defining
> by fiat the semantics for doing template floating-point arithmetic, but
> the committee didn't think it was worth the effort. It's the sort of
> thing that Ada goes through with its universal floats, but at least
> there the application is of wider use.

We are talking not about floats, but about the principle of matching by
content. There is no any chance to hold on it:

   template <p> void foo<HALT(p)> ...

>> I don't see what systems programming has to do with templates.
> 
> C++ was written as an enhancement for people already using C. It gave
> those people a great deal of extra expressive power, but they would not
> have given up what they already had.

This is a different statement, which sounds a bit silly in the context of
the thread. Basically it is - many who learned C as the first language were
so devastated by this experience, so it would be just inhumane to ask them
to lean anything else. For this reason they must face that horror time and
again. I cannot judge. I am not a psychoanalytic, nor C was my first. (:-))

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de