Waldek Hebisch <[EMAIL PROTECTED]> writes: > Martin Rubey wrote: > > > > Dear all, > > > > it occurred to me (perhaps it's obvious) that we could add provisos in a > > rather > > straightforward way to FriCAS, namely through an Operator "Cond". Perhaps > > this > > is not ideal performancewise, but I think it could be a first step into a > > good > > direction. > > I am not sure if it is obvious, but I had this in mind when I wrote > about conditional expressions. However, I think that name "conditional > expression" is better -- when Tim wrote about provisos he was short > on details but he indicated possible implementation technique > which IMHO is not practical. OTOH conditional expressions are > used by other systems (I am not sure the name is accepted one).
Yes. I used "provisos" (under quotation names) only to make archive search easier. > > Cond would be a list with every second element being an expression, every > > other > > the condition when it holds. > > Little nitpick: list of pairs (condition, expression). Yes. Currently BasicOperator's want a list of expressions, but pretend let's you change this... > > To get started, the most tricky part is probably to implement the basic > > ring operations properly? > > > > Ring operations are easy: > > [c_1, e_1],...,[c_n, e_n]] op [[c'_`, e'_1],...] > > is the list > > [c_1 and c'_1, e_1 op e'_1], [c_2 and c'_1, e_2 op e'_1],...] > > that is we for logical and for all pairs of conditions > and perform operation on corresponding expressions. But this will give a huge mess... > Tricky part is simplification, especially simplification of > conditions. One obvious simplification is if c_1 and c_2 > are both ands with common factor, then we do not duplicate > the factor. Another is that we combime pairs where > both expression and condition are equal. Without > such simplifications size of expressions would grow > exponentially without bound. With those to simplifications > if we start from some fixed set of conditions we will > saturate when we get all products (still exponential, > but may be reasonable in practice). OK. > Ideally we want more simplifications (like detection > of impossible cases), but the two above are probably > enough to start implementation. Well, what is a suitable language for conditional expressions to get this started? Actually, it might be worth to have a domain for conditional expressions... Martin --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/fricas-devel?hl=en -~----------~----~----~----~------~----~------~--~---
