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=3.8 required=5.0 tests=BAYES_00,INVALID_MSGID,
	RATWARE_MS_HASH,RATWARE_OUTLOOK_NONAME autolearn=no autolearn_force=no
	version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,c462e8ad74872a98
X-Google-Attributes: gid103376,public
From: "Jerry van Dijk" <jvandyk@ibm.net>
Subject: Re: Question on modular types
Date: 1997/01/06
Message-ID: <01bbfbf8$4fda7a40$5f2d5c8b@jerryware>#1/1
X-Deja-AN: 208096116
references: <01bbfa96$66d516a0$8d2d5c8b@jerryware> <dewar.852430006@merv>
organization: *JerryWare HQ*, Haarlem, Holland
newsgroups: comp.lang.ada
Date: 1997-01-06T00:00:00+00:00
List-Id: <comp.lang.ada>



Robert Dewar <dewar@merv.cs.nyu.edu> wrote in article
<dewar.852430006@merv>...

>> "Clearly, all values are invalid, and that without inporting any
>> values from the outside world."

> No! If it is clear to you, you need your Ada prescription fixed :-)

Mmmm, I'm afraid if I asked my docter for that, I might wind up with a
totally different prescription... :-)

>   A := -1;

> -1 is not a literal here, it is an expression, and the unary minus
> operator is a modular unary minus. This is a useful, intended, and
> clearly documented facility.

Yes, I found it:

4.5.4(3): For modular integer types, the unary adding operator -, when
          given a nonzero operand, returns the result of subtracting
          the value of the operand from the modulus; for a zero
          operand, the result is zero.

   type Byte is mod 256;
   A_Byte : Byte;

   A_Byte := -1; -- means A_Byte := Byte (Byte'Modulus - 1);

However, 4.5.4(1) mentions that all unary adding operators have their
conventional
meaning, and since the note is not technically part of the standard,
that leaves
me wondering wat that 'conventional meaning; might be. And
'conventional' to whom ?

Thanks,
Jerry.