Class of User Types [Was: Moving code from octave-forge to octave [Was: polyderiv problem?]]

[David Bateman]

> How do you save and load such beasts from files?
>
> Does typeinfo give more complete information?
>
> If the types really are not compatible, then the string names should 
> not match.
>
> Maybe class should return "GF(2)" if it is GF(2), and octave can pass the
> extra info in the parentheses to the zeros constructor.
>
> - Paul
Paul,

load/save is no problems, I just save which extension field of GF(2) I'm 
in an the primitive polynominal, together with the class. Its just 
another piece of information associated with the variable.

As for having class return all of the information on the type, I really 
hope your kidding. The problem is then that there are a huge number of 
different primitive polynomials available as we take larger extension 
fields of GF(2). For example GF(2^15) has 1800 different possible 
primitive polynomials. The problem is even worse for fixed point types, 
where each element of a matrix can have a different representation and 
each of those between 0 and 32 bits in the representation of the integer 
and decimal parts of the elements.

The implication that class returns the full information to define the 
type, is that there is a completely different type for all possible 
galois fields and fixed point matrices. Even if there were seperate 
types for each of the possibilities, imagine the number  of  different 
versions of the operators I'd need to implement, particularly for the 
fixed point types. In all practical senses this is not feasible.

For the fixed point types, having different representations doesn't make 
them incompatiable. All aritmetic operators can still be performed. 
However the same can not be said for galois fields. So I think for 
galois fields we just have to live with the return string of class being 
the same for incompatiable galois fields...

Regards
David

--
David Bateman                                address@hidden
Motorola Labs - Paris                        +33 1 69 35 48 04 (Ph) 
Parc Les Algorithmes, Commune de St Aubin    +33 1 69 35 77 01 (Fax) 
91193 Gif-Sur-Yvette FRANCE

The information contained in this communication has been classified as: 

[x] General Business Information 
[ ] Motorola Internal Use Only 
[ ] Motorola Confidential Proprietary