On Thu, Oct 1, 2015 at 12:00 PM, Bill Page <bill.p...@newsynthesis.org> wrote: > On 1 October 2015 at 14:23, William Stein <wst...@gmail.com> wrote: >> ... >> One other impression you have is that categories were just bolted on >> by combinatorics people at the end. However, David Kohel and I >> actually implemented the first round of category-related stuff in Sage >> right at the very, very beginning -- it was one of the first things we >> did, motivated by what David had wished Magma had. > > The concept of "parent" is adopted from Magma, right? I am not sure I > really understand it, either relative to the usual inheritance rules > in Python or category theory. Clearly the related? concept of > "element" is borrowed from category theory - maybe even topos theory?
Yes, parents and elements are from Magma. To me they have nothing to do with category theory. Category theory is one level up, and is about abstracting away from thinking about parents and elements (and instead thinking about objects, morphisms, and functors). Just as Bill Hart said, the parent/element approach in magma is very useful, and inspired Sage and Nemo, but isn't category theory. > Is there a reasonably short description of categories in Sage "for > category theorists"? No idea.... > >> And it is has >> just been iteratively refined over the users, with Nicolas Thiéry >> doing by far the most work on it during his sabbatical a few years >> ago. There was also a lot of input coming from the multiple rounds >> of rewriting of the coercion model, by me, David Roe, Robert Bradshaw >> (especially), and others. >> > > Do you consider the coercion model as part of or motivated by category > theory in Sage? Yes, very much so -- that's the part I worried about more. Though another motivation is for category theory is better code sharing (that's more of the part that Nicolas added). -- William -- William (http://wstein.org) -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
