Jacques Carette <[EMAIL PROTECTED]> writes: > In other words, we are not so much interested as implementing Species as with > replacing inductive datatypes (ie polynomial Functors and their > least-first-points) with Species as the basic language.
I must admit that I do not know what an inductive datatype is... > One question: do you plan to implement operations akin to Maple's combstruct, > in particular random generation? Although I would very much like to have that, I do not really know yet how to go about it. Note that for ordinary species, i.e., functors from finite sets to finite sets, you do not have any order on the "input set", nor on the "output set", i.e., the set of structures. On the other hand, at least as far as I know, random generation usually works via ranking and unranking algorithms, which assume that at least the output set is ordered. I'm not saying that it's impossible to fit this nicely into the species framework, but I do not know how to do it yet. Input would be greatly appreciated, of course. To make things clearer: combstruct and MuPAD-Combinat really had "usability" as primary goal. As one consequence, they do not implement species, but rather "combinatorial classes", that is, collections of objects with a size function. The main drawback of that method is that you cannot treat labelled and unlabelled objects uniformly, there is no such concept as an isomorphism type, which, in my opinion, is the main strength of (ordinary) species. In that sense, combinatorial classes are very close to linear species. As a consequence, their implementation of "unlabelled composition" does not give what somebody used to species would expect. (WARNING: Compose in aldor-combinat/trunk is also broken with respect to isomorphismtypes! You'd have to use the iso-experiment branch instead...) Martin ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Aldor-combinat-devel mailing list Aldor-combinat-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/aldor-combinat-devel
