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From: mab@wdl1.wdl.loral.com (Mark A Biggar)
Subject: Re: "Subtract C, add Ada"
Message-ID: <1995Jan26.185121.29955@wdl.loral.com>
Sender: news@wdl.loral.com
Organization: Loral Western Development Labs
References: <3fode9$dap@soleil.uvsq.fr> <lawnm.33.00146988@leeds.ac.uk>
 <3g7ame$5d8@Starbase.NeoSoft.COM>
Date: Thu, 26 Jan 1995 18:51:21 GMT
Date: 1995-01-26T18:51:21+00:00
List-Id: <comp.lang.ada>

In article <3g7ame$5d8@Starbase.NeoSoft.COM> smize@Starbase.NeoSoft.COM (Samuel Mize) writes:
>It seems to me that something more general would be useful,
>along the lines (NOT THIS SYNTAX, THIS IDEA):
>
>     foo( bar( zot( element + 1))) := <left> * ( <left> + 3 );

That's what rename is for and it's more powerful to boot as you can choose
exactly what parts of your expression get short names, For example:

declare
	Left: Interger renames foo(bar(zot(element+1)));
begin
	Left := Left * (Left + 3);
end;

but also:

declare
	Index: Integer renames bar(zot(element+1));
begin
	foo(Index) := foo(Index) * ( foo(Index) + 3);
end;

You may well want to use the second case, if that documents your algorithm
better.  Note that a good compiler probably produces identical code for
both examples assuming good common expression elimination.

--
Mark Biggar
mab@wdl.loral.com