Re: Ichibah flames, and flames out over, Ada 9X

[firth@sei.cmu.edu (Robert Firth)]

In article <1993Mar15.231916.16276@ennews.eas.asu.edu> koehnema@enuxhb.eas.asu.edu (Harry Koehnemann) writes:

>And look how the word "access" has completely removed "pointer" or
>"reference" from existence in the CS world :).  But really, why take a
>very well understood concept and name it something completely off the
>wall.  Didn't Ada desire to facilitate understanding, rather than get
>in it's way?

I'll answer that.  The main reason we used "access" instead of "pointer"
is that "access" is a semantic concept at the level of the language, while
"pointer" is an implementation technique at the level of the underlying
machine.

We had seen the hideous confusion this mistake had caused in other
languages, leading to wrong code, unmaintainable code, and non-portable
code.  Examples of false assumptions caused by the "pointer" terminology
include

	. an access value is a machine (hardware) address
	. an access value and an integer are interconvertible
	. access values with different base types are interconvertible
	. all access values are the same physical size
	. arithmetic on access values can be used in lieu of proper
	  high-level iterators

To anyone familiar with Ada, these propositions are blatantly false.
Replace "access" with "pointer" and they remain false, but almost
invisibly so.

One goal of Ada was reliable programming.  In our opinion, the use of
"pointer" terminology was a major source of almost ineradicable design
and implementation errors in much then current software.  I believe
history has vindicated us.

Robert Firth