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From: Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>
Newsgroups: comp.lang.ada
Subject: list strawman
Date: 06 Jan 2002 15:55:50 -0500
Organization: NASA Goddard Space Flight Center
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I've done a priliminary implementation of
http://www.telepath.com/dennison/Ted/Containers-Lists-Unbounded.ads.html
using SAL lists as the base. It implements fully
safe iterators. The sorting nested package is not implemented, mostly
because I didn't have time, but also because there are some design
issues (I'll talk about that in a separate post).

See http://users.erols.com/leakstan/Stephe/Ada/strawman-sal.html to
Download my the source. It relies on a slightly modified version of
SAL (two added functions); if you want to actually compile it, either
add the functions yourself (should be obvious), or send me an email.

There is only a simple test; it demonstrates the operation of "&".
But it uses an iterator to print the lists, so it's actually a good
test. I'll try to use Ted's test harness when that is ready.

This was an interesting excersize. I got quite stuck on making the
iterators safe, while at the same time not requiring the user to use
'Unchecked_Access. A hint from http://homepage.ntlworld.com/ramatthews/
(Robert A. Matthews' GAPSE) set me straight; use a layer of indirection.

There are three source directories: Iterator_1, Iterator_2, and
Source. The Iterator directories show early attempts at implementing
safe iterators; the file "iterator_design.text" describes the attempts
and the final result.

The final implementation is quite complex (and I haven't done sort
yet). I don't think I will ever use this package in a real project.
Just writing all the tests to prove that iterators actually are safe
will take quite a while. But it is an interesting example of what can
be done.

-- 
-- Stephe