From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,a1ce307c10055549
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2002-12-17 06:51:45 PST
Newsgroups: comp.lang.ada
Path: 
 archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!uunet!sea.uu.net!sac.uu.net!ash.uu.net!world!news
From: Robert A Duff <bobduff@shell01.TheWorld.com>
Subject: Re: calenday (was Re: IBM Acquires Rational Ada
User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2
Sender: news@world.std.com (Mr Usenet Himself)
Message-ID: <wcc8yyopum7.fsf@shell01.TheWorld.com>
Date: Tue, 17 Dec 2002 14:50:40 GMT
Content-Type: text/plain; charset=us-ascii
References: <mailman.1040104682.11706.comp.lang.ada@ada.eu.org>
NNTP-Posting-Host: shell01.theworld.com
Mime-Version: 1.0
Organization: The World Public Access UNIX, Brookline, MA
Xref: archiver1.google.com comp.lang.ada:31955
Date: 2002-12-17T14:50:40+00:00
List-Id: <comp.lang.ada>

"Grein, Christoph" <christoph.grein@eurocopter.com> writes:

> > > Yes, but if what you want is "to work with the day of the week in
> > > the form of a number", why use Unchecked_Conversion when
> > > day_name_type'Pos does what you want without further ado?
> > Suppose you have an array of day_name_type that you want to
> > convert to an array of numbers.  It's much cheaper to use
> > Unchecked_Conversion than it is to loop through the array and
> > call the 'Pos function or the 'Val function on each element of
> > the array.
> 
> This seems unbelievable with RM 13.4(8) in mind.

I don't buy the unchecked-conversion-of-array efficiency argument.
It might be true that unchecked conversion of an array is faster than
a loop with 'Pos.  And unchecked conversion of a *pointer* to the array
would certainly be faster.  But there is no need to resort to such
low-level hackery.  Keep arrays of Day_Name_Type.  Whenever you need to
process a particular day using arithmetic, use 'Pos and 'Val.  There is
never a need to have an array of days-as-integers, and there is never a
need to do a whole-array conversion.

Note that 'Pos and 'Val should generate zero machine code,
if you stay away from enumeration representation clauses.

- Bob