CAUTION, thinking out aloud ahead... Tracy,
Verbs pwrset (Fraser+Kip) and powSet (Raul) temporarily impose the "numerical" order of the masks used to find elements of the power set, then provide the standard "lexical" order by applying /:~ . The masks do not destroy sorted-ness or nubbed-ness which is already present in the argument set. _When_ does your "sort whenever some function takes a set as an argument" take place? How does a program know _where_ to recurse a sort nub? (Thinking about sets some of whose elements are sets some of whose ...) Like you, I am not trying to be argumentative. I'm trying to think about mathematically equivalent to _what_ ? I shudder at the task of figuring out what the task is, and opt for appropriate "sort nubs" (Fraser's verb Set) as the argument set is being created and as the value set is being created. Try to use operations which _preserve_ the property of being recursively sorted and nubbed. (_preserve_ as contrasted to _impose_) This is thinking out loud, thanks for listening. Kip Tracy Harms wrote: > On Mon, Aug 3, 2009 at 6:15 PM, Kip Murray<[email protected]> wrote: >> Do J sets need to be ordered? Fraser believes not, and I will try to >> persuade >> him otherwise following his note below. >> > > Kip, > > In the implementation of set-math in J it is necessary to order the > representations of sets. I don't see any problem including this step > "at creation" of each set, but it's mathematically equivalent to sort > (or even cull duplicates) whenever some function takes a set as an > argument. The need to sort is a side-effect of a language feature in > J: J imposes an ordering on all collections by having a single > datatype (array). Sorting each thing that represents a set is just the > easiest way to compensate for that inherent structure. (<--YES -- Kip) > > In saying that, I don't think I've contradicted or corrected anything > you've said. I think I'm making roughly the same point. > > Tracy ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
