Re: Equality operator overloading in ADA 83

[bobduff@world.std.com (Robert A Duff)]

In article <mheaney-ya023680002704970206040001@news.ni.net>,
Matthew Heaney <mheaney@ni.net> wrote:
>But people need to be taught that there are
>o  static strings - whose length is fixed, and determined statically (eg Pascal)
>o dynamic strings - the length of string objects are fixed, but are
>determined dynamically (eg Ada)
>o flexible strings - the length of string objects can change (Algol 68)

I always thought "dynamic" meant what you call "flexible".  Too bad the
software industry doesn't agree on terminology very well.

>I have had a similar experience.  I always have to remind programmers to
>declare constants instead of variables.

IMHO, a better language design would be to make objects constant by
default, and stick in an extra keyword when you want variable.  Ada does
it the other way 'round.

How about a compiler warning for variables that could have been
constants?

>This declares a constant object, using assignment.  But why?  Couldn't one
>bind O to a value, w/o using assignment, similar to a LISP let expression? 

Yeah, I've done some thinking about that, and I suspect something along
these lines would make a lot of sense.

>   The_Iterator : Stack_Iterator'Class (Stack'Access) := 
>      Iterator (Stack);   -- not legal Ada

I'm not sure why you want to mention Stack twice.

Why not have the initialization code for your iterator type do the
necessary stuff (and not use a class-wide iterator)?  Would that work?

Note also that Ada 95 allows:

    X: T renames F(...);

even if T is a limited type.  X is constant here, though.

- Bob