Hi Simon, On Jan 10, 11:33 am, Simon King <simon.k...@nuigalway.ie> wrote: > Well, that's a default method, i.e., if nothing else is implemented > than a conversion by strings is attempted, because there is some hope > that the result makes sense. > > So, a proper way would be to override the default sage() method (from > pexpect, or where is it defined?) for the gap interface.
I think the method called is in interfaces/expect.pyc but I am not sure about that. > This new method would test the type of gap data (matrix; permutation > group element; conjugacy class, ...) and do whatever needs to be done > (return a sage matrix; return a permutation; return an instance of the > new "conjugacy class" class, ...). Only if an unknown data type > occurs, a string conversion would be attempted, as a last resort. If > it fails, then nothing can be done. The problem, as I see it, is that AFAIK gap has no "type checking" to tell what kind of object we are dealing with (if there really is such a method, I'd love to be corrected!). > I don't know how to properly test the data type in gap. Would one use > functions like IsPermGroup, IsMatrix? > > So, if IsMatrix is true for a gap object M, then the next step is to > determine the underlying ring (dunno how). If R is that ring, then > M.sage() would return a matrix over R.sage(). For the particular case of matrices that might actually work. Since gap's IsMatrix ensures that all the entries belong to a common ring (beyond checking the lists have the right size) we only need to check the base ring of one of the elements, for instance the [1,1], which is always going to be there: sage: h = matrix(GF(5),2,[1,2, -1, 1]) sage: hh = h._gap_() sage: hh.IsMatrix() true sage: hh[1,1].Ring() GF(5) So, lacking a better choice we could just make a list of distinguished objects in which to apply ad-hoc conversion methods. Cheers J
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