Re: calenday (was Re: IBM Acquires Rational Ada

["Warren W. Gay VE3WWG" <ve3wwg@cogeco.ca>]

Bill Findlay wrote:
> On 16/12/02 21:41, in article
> mailman.1040074922.28258.comp.lang.ada@ada.eu.org, "David C. Hoos"
> <david.c.hoos.sr@ada95.com> wrote:
> 
> [snip]
> 
>>>>>On 16/12/02 18:38, in article 3DFE1D97.6020109@cogeco.ca, "Warren W.Gay
>>>>>VE3WWG" <ve3wwg@cogeco.ca> wrote:
>>>>>
>>>>>>I would suggest one more small point WRT to:
>>>>>>
>>>>>>type day_name_type is (mon,tue,wed,thu,fri,sat,sun);
>>>>>>
>>>>>>Add a representation clause to guarantee that the values
>>>>>>start with sun => 0, mon => 1 etc.  For some code, it is
>>>>>>much easier to work with the day of the week in the form
>>>>>>of a number.
>>>>>
> 
>>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.
> 
> Isn't mon => 0, ..., sun => 6 guaranteed to be the
> encoding of this type in any case, even without a
> representation clause?
> 
> Defining sun => 0, mon => 1, inconsistently with 'Pos, is going
> to create a distributed inefficiency in processing this type.
> 
> Can you see this being worth the hypothetical saving in unchecked array
> conversion? (We are discussing unconditional advice here.)

Actually, I was not thinking of Unchecked_Conversion when
I suggested the representation clause. You are right in that
the 'Pos(mon) is zero anyway (I didn't know that this was
guaranteed by the language). It is also apparently bad
practice to rely on the representation, because I get the
impression that some Ada compilers may ignore the representation
clause.

My question now is, why is Monday first?  My own personal
preference would be to have Sunday first to be consistent
with the UNIX practice in the use of localtime/gmtime and
mktime(3C) routines.

Was there a reason that Monday was chosen as the first in
this series?

TIA, Warren.
-- 
Warren W. Gay VE3WWG
http://home.cogeco.ca/~ve3wwg