Hi, On Mon, Feb 11, 2019 at 11:14:35AM +0100, Jeroen Demeyer wrote: > On 2019-02-11 11:12, David Coudert wrote: > > > > > > Le mardi 29 janvier 2019 23:19:12 UTC+1, Thierry (sage-googlesucks@xxx) > > a écrit : [...] > > > > That said, regarding the .edges() method, i think that returning a list > > of pairs is a very wrong approach (though this is what is done for > > years). Indeed, a list is not only an iterator, but also a > > container. In > > particular: > > > > (a,b) in G.edges() > > > > is a syntaxially correct statement, but it is far from equivalent to: > > > > G.has_edge(a,b) > > > > Which is extremely misleading and can lead to silent mistakes > > (personally, i used lot of hand-made reorderings in my pyograms > > before i > > discovered has_edge). > > > > Here i would advocate that G.edges() returns a *view* on G, with a > > dedicated __iter__ method corresponding to the edge_iterator method and > > a __contains__ method corresponding to the has_edge method. By having a > > view, you will save a lot of time and memory, and have the benefit that > > it will follow the graph's mutations. > > > > > > This is an interesting idea, although I'm not sure how to implement that > > efficiently. > > I don't see why it should be inefficient (assuming you implement it in > Cython of course).
Actually, a view is somehow pointing to an existing object, so it is O(1), to be compared to contstructing a list which is O(|E|). Ciao, Thierry -- 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 https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
