Karim BELABAS on Wed, 12 Jun 2002 19:02:53 +0200 (MEST)

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Re: 22- polgalois()

> From: John Jones <jj@asu.edu>
>  > On Sun, 9 Jun 2002, Karim BELABAS wrote:
>  >> 22- INCOMPATIBILITY: polgalois(); changed 3rd component of result so that
>  >> it gives the numbering among all transitive subgroups of S_n [ was ad
>  >> hoc up to 7, then as described above for n >= 8 ]
>  > Unfortunately, it will break existing scripts
> Since you asked for opinions, here is my two cents.  You are changing
> a documented behavior which has been in effect for what, 10 years?
> And, you are planning on doing it on a change in minor version, and
> without a variable to control which form would be used.
> IMHO, a change in minor version change should not break correctly
> written scripts.  At least, that has been the philosophy of other
> software projects I have used.  So, I think the right way to implement
> a change like this would be to offer both naming schemes, default to
> the old way, document the old way as deprecated, and offer a variable
> to switch to the new behavior.  It would not be enough to put the
> change into one of the existing categories of the compatibility
> variable.  Correctly written scripts would break if they were written
> to conform to the documentation.

I fear this is quite convincing.

OK, I've undone the polgalois() change, so that the old naming scheme is back
in effect (sigh). There's a new boolean default new_galois_format: if set to
true, you'll get the new format [set to false = 0] by default. I will
eventually set it to true, someday.

There's a global variable

  int new_galois_format = 0;

which you can set to 1 for the same effect in library programming.

Karim Belabas                    Tel: (+33) (0)1 69 15 57 48
Dép. de Mathematiques, Bat. 425  Fax: (+33) (0)1 69 15 60 19
Université Paris-Sud             Email: Karim.Belabas@math.u-psud.fr
F-91405 Orsay (France)           http://www.math.u-psud.fr/~belabas
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