Re: bnfinit question

[Karim Belabas <Karim.Belabas@math.u-bordeaux.fr>]

* Ian G Connell, Prof [2018-08-16 18:02]:
> When the number field is too big, for example in a script read
> 
> by pari-gp
> 
>  b=bnfinit(122901+5*W+W^2+W^4);
> 
> b.fu gives the warning: ..too large, not given
> 
> Is it possible to write commands in the script so that when this
> 
> happens, b.fu is given a special value such as 0?

Hum. Currently, b.fu operates as follows :

Check the content of b[8][5]
- if "empty" (encoded by the sentinel value [;], the empty matrix),
  raise an exception;
- else return the units.

I don't see a problem with changing this behaviour to have b.fu return [;]
under GP, instead of an exception. (This can be done without affecting
standard libpari functions, only member_fu needs to be changed.)

In the meantime, the only solution is to directly check b[8][5] to avoid the
exception ...

Cheers,

    K.B.
--
Karim Belabas, IMB (UMR 5251)  Tel: (+33) (0)5 40 00 26 17
Universite de Bordeaux         Fax: (+33) (0)5 40 00 21 23
351, cours de la Liberation    http://www.math.u-bordeaux.fr/~kbelabas/
F-33405 Talence (France)       http://pari.math.u-bordeaux.fr/  [PARI/GP]
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