[GAP Forum] Low Index Subgroups Process.

[Joachim Neubueser]

Dear Michael Hartley,

You wrote to the GAP Forum:

> One thing I miss from CAYLEY (now MAGMA) is the existence of a
> collection of functions that returns the low index subgroups of a
> finitely presented group one by one instead of all at once. This was
> particularly useful in situations where one is searching for an example
> of a low index subgroup with certain properties, but returning the
> complete list of subgroups up to the required index would just take far
> too long.
> 
> Well, I have hacked the source code of the LowIndexSubgroupsFpGroup
> function, and created two functions 
> "LowIndexSubgroupsStream" and "GetNextLowIndexSubgroup". They are in
> the attached file, and may be used as follows:

Thank you for your letter and the proposal made in it. 

I agree  that such extension  of the functionality of  LowIndex method
would  be useful.   In an  internal discussion  remark on  your letter
Thomas Breuer came forward with an idea of some technical changes that
might improve the working of your  ideas within GAP.  We would like to
discuss this further with you.

Unfortunately the promised 'attached  file' did not reach us, possibly
due to the mechanism of distribution  of mails to the GAP Forum. Could
you please send these attachments directly to my address.

While, as said, we are interested  in your proposal and want to get it
available in GAP, please understand that  it may take a little time to
get down to it, since people  such as Thomas have a number of projects
under work.

Thanks again and kind regards    Joachim Neubueser

PS:  It should  be  clear that  we  are talking  about realizing  your
proposal in GAP, we have nothing to do with the development of Magma.