On Dec 29, 2008, at 4:15 PM, William Stein wrote: > On Mon, Dec 29, 2008 at 2:43 PM, Justin Walker <jus...@mac.com> wrote: >> >> On Dec 29, 2008, at 5:23 PM, John Cremona wrote: >> >>> >>> Maybe I missed the point here but after >> >> The point was a minor one... >> >>> R.<x1,x2>=QQ[] >>> M=matrix(R,1,2,[x1+x2,x1*x2]) >>> >>> you can get at the entries like this: >>> sage: M[0,0] >>> x1 + x2 >>> sage: M[0,1] >>> x1*x2 >> >> For the OP, it was surprising that "list(M)" did not return a list of >> the entries of M. The reason is that (for Python, I think), M is a >> list of "rows". The expression "M.list()" does return a list of the >> entries of M, which is what one might naively expect of the former >> expression. >> >> In the world of objects, its not always clear what the object is, I >> guess. >> > > If X is a python object, then list(X) literally makes the list list > X[0], X[1], etc., until the Python interpreter gets and IndexError. > It doesn't call "X.list()". > > I think that list(X) and X.list() are different for matrices is an > unfortunate inconsistency. The best fix I can think of would be to > eliminate the list method entirely, and have a method > X.list_of_entries() or X.entries(). Just changing .list()'s > definition would be dangerous, since a lot of code probably depends on > the current definition. Changing list(X) to behave differently would > likely require making X[0] return the first entry of X rather than the > first row, which would be really confusing.
+1 to (deprecating then removing) removing X.list(), and replacing it with X.entries(). > That X[0] returns the first row instead of the first column is a > completely arbitrary choice. It had to be made, so it was made. I don't think it's quite arbitrary, M[a][b] == M[a,b] seems a lot more natural than the other way, and the latter ordering, though perhaps arbitrary, seems to be the more conventional one. - Robert --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
