Re: Question on modular types

["Jerry van Dijk" <jvandyk@ibm.net>]

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.