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=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,ca9eef4d5e2078ea
X-Google-Attributes: gid103376,public
From: Ken Garlington <kennieg@nospam.flash.net>
Subject: Re: Beware: Rep spec on an enumeration type causes code explosion
Date: 1997/12/12
Message-ID: <3491E0BF.3D18@nospam.flash.net>#1/1
X-Deja-AN: 297711349
References: <gwinn-0812971210080001@dh5055133.res.ray.com>
 <EKxx9n.Ly1.0.-s@inmet.camb.inmet.com> <348F3DFC.10DB@nospam.flash.net>
 <3490252D.6B550F17@ac3i.dseg.ti.com> <3490B7B1.711A@nospam.flash.net>
 <mheaney-ya023680001212970109560001@news.ni.net>
Reply-To: Ken.Garlington@nospam.computer.org
Organization: Flashnet Communications, http://www.flash.net
Newsgroups: comp.lang.ada
Date: 1997-12-12T00:00:00+00:00
List-Id: <comp.lang.ada>


Matthew Heaney wrote:
> 
> In article <3490B7B1.711A@nospam.flash.net>,
> Ken.Garlington@nospam.computer.org wrote:
> 
> >>       Contiguous := Contiguous_Type (Holey);
> >>       -- implicitly does equivalent of 'Pos
> 
> >This assumes Holey will always be one of A, B, C, D, E. What happens
> >when the underlying
> >I/O device returns a value of 6 for Holey?
> 
> Of course, you must always check for validity prior to the conversion,
> 
> if Holey'Valid then
>    Contiguous := Contiguous_Type (Holey);
> else
>    <handle error>
> end if;

which is the same as my original statement, to wit: "One of the nice
things about 'holey' representations in Ada, when used for interfacing
to external systems, is the use of 'Valid to check for valid input data
in a very readable manner. However, I would convert the raw input to a
non-holey type after the check, using either a map or case statement
(depending upon the compiler)."

A response to this statement was: "There is no need for anything so
elaborate." The corresponding code did the conversion without a
check, which prompted me to ask how validity was handled.

> --------------------------------------------------------------------
> Matthew Heaney
> Software Development Consultant
> <mailto:matthew_heaney@acm.org>
> (818) 985-1271