Re: Software Engineering News Brief

[fjh@mundook.cs.mu.OZ.AU (Fergus Henderson)]

dewar@merv.cs.nyu.edu (Robert Dewar) writes:

>Paul Eggert says
>
>"... which is why the next version of Ada should support Gregorian dates
>all the way back to at least the year 1, if not before.  Trying to
>match the historical introduction of the Gregorian calendar
>leads to severe politico-technical problems.  For an example of this
>see my May 1995 comp.risks article about Sybase's historically naive
>practice of arbitrarily rejecting Gregorian dates before 1753."
>
>That sounds silly to me. This is a highly specialized requirement that
>should be provided by auxiliary packages, not by the central package
>for dealing with near by dates that is primarily intended for use in
>control of time related processing (note that Calendar is still in the
>tasking chapter, even in the new RM.

I don't think it is a highly specialized requirement.  I think the
requirement for a generic date type the works over a large range of
dates is quite common.  Many programs let users enter dates, and
putting strict requirements on the dates entered is not unlike assuming
that no-one will ever want to enter a line with more than 80 characters.

>Also, Gregorian dates are quite tricky, because the change over in the
>calendar happened at different times in different parts of the world, so
>you need detailed geo-political localization for such processing.

Gregorian dates aren't tricky, the change-over from other systems is tricky.
That's why Paul Eggert suggested supporting Gregorian dates only, even
for dates before the Gregorian system was used.

>I would say this is a perfect example of
>specialized needs that should NOT be met in the standard language. I would
>far rather have Ada implementors working to get their implementations more
>efficient and more robust than wasting time in the library trying to figure
>out when the switch to Gregorian dates happened in Lithuania.

You misunderstood what Paul Eggert was saying.  His suggestion would *not*
require implementors to figure out when the switch to Gregorian dates
happened in Lithuania or anywhere else.

--
Fergus Henderson <fjh@cs.mu.oz.au>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh@128.250.37.3         |     -- the last words of T. S. Garp.