On Fri, Jun 1, 2012 at 6:07 AM, Jeffrey Johnson <n3...@me.com> wrote: > I asked 2 very specific questions … the rest is quite important also, > but I need to understand precisely what properties set:versions have in order > to implement correctly (and I don't fully understand your reply). > > Specifically: > > 1) Is the set:versions VERSION independent of the order of the > calls to rpmsetAdd()? (you know the routine as set_add())
Completely independent - you can add symbols in any order. The symbols are then hashed and sorted by their numeric values. The underlying idea is that a set-version is just a (sorted) set of numbers. You can add whatever symbol to it, possibly twice, the symbol will be hashed to a number, in a unique manner, and finally you can get the string representation of the set of numbers. This involves much fuss under the hood, but basically, you should think of the set of symbols, which is just the set of numbers, after each symbol has been hashed individually. > 2) Can the set:versions encoding be compared for more than equality? > What set/arithmetic property is the basis for the comparison? What > circumstances/constraints are there related to > … You cannot always compare > set-versions in terms of "greater or equal" (but when you can, > it's > important). Set-versions compare as sets. There are Euler diagrams to visaulise set comparsion, which is an undergraduate matetrial. The idea is that, real numbers are linear order: you can always tell either V1<V2 or V1>=V2. Sets are quite another matter: you cannot always apply for "tertium non datur" (either lt or ge). Which is to say that sets can be quite different and do not compare easily. The order can be imposed on the sets, though, by requiring the "greater" sets to have at least the same elements they compare against (perhaps I'm starting to retell the undergraduate material, which is not going to last). To sum up, there IS a mathematical basis behind "Requires: foo >= set:asdf" dependencies. > I can of course answer my own questions with try-and-see test cases. ______________________________________________________________________ RPM Package Manager http://rpm5.org Developer Communication List rpm-devel@rpm5.org
