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From: Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Problem implementing Iterators
Date: Tue, 27 Jan 2015 13:58:38 -0700
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Xref: news.eternal-september.org comp.lang.ada:24766
Date: 2015-01-27T13:58:38-07:00
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On 01/27/2015 11:43 AM, Björn Lundin wrote:
> 
> As I understand it, its only purpose is to tell the programmer that
> this variable may be changed via pointers - beware ...

My understanding is that there are certain optimizations that can be taken with
unaliased objects that cannot be done with aliased objects, so this provides
important information to the compiler.

Some time ago (late 1980s or early 1990s) there was an article in /Ada Letters/
about why the Tartan Ada compilers were able to produce faster code for Ada
versions of their C benchmarks than their C compilers. The fact that all C
variables are aliased, while all Ada-83 variables are not, was one of the factors.

-- 
Jeff Carter
"When Roman engineers built a bridge, they had to stand under it
while the first legion marched across. If programmers today
worked under similar ground rules, they might well find
themselves getting much more interested in Ada!"
Robert Dewar
62