On Sun, Aug 2, 2009 at 2:00 PM, William Stein <wst...@gmail.com> wrote:
> > On Sun, Aug 2, 2009 at 9:13 AM, Robert Dodier<robert.dod...@gmail.com> > wrote: > > > > Robert Bradshaw wrote: > > > >> Sage lists are Python lists, which are very different than > >> Mathematica lists. > > > > You say that as if it's a fact of geography which can't be changed. > > > >> to change all lists would be a massive (backwards- > >> incompatible) change, as well as another step away from Python. > > > > Not exactly. At present something like 1 + [2, 3, 4, 5] causes Python > > to cough up an error, right? So extending arithmetic operators to > > lists wouldn't change the behavior of any existing Python program. > > (I'm not worried that someone might have written a program which > > requires an error to be triggered when number + list is encountered.) > I think Robert has a good point here: infix operations between numbers and lists wouldn't break any Python code, because this kind of constructs are not supported in pure Python. However, it could add a lot of readability and programming easiness to Sage because a common task as a scientist is to manipulate and transform a lot of data and (I think) the most basic container to do that is a list. > Unfortunately for your suggestion, arithmetic operators are methods of > the objects. To make "1 + [2,3,4,5]" and "[2,3,4,5] + 1" not raise an > exception would require changing the Python interpreter itself, at the > C level. True, but I think it's possible to catch all this things with the preparser and make them work as expected, as I suggested before. Is it possible and worth the try? I would want to do it when I have some spare time. Carlos > > > > You could even pitch it in algebraic terms. The set of lists comprises > > an ideal in the ring of ... well, of something. Maybe the ring of > > all numbers and lists. Anyway maybe that would appeal to someone > > with an algebraic state of mind. > > > >> Of course, we support all of this without numpy as well. > >> > >> sage: a0 = vector([1,2,3,4]) > > > > That's not enough. Only vector + vector, scalar * vector, and > > inner product are defined, right? I'm pretty sure users would > > like to see vector * vector, vector ^ exponent, scalar / vector, etc. > > > > With all that said, Mathematica is more than a little confused > > about lists --- there is no distinction between lists and sets, and > > a matrix is just a list of lists. That's a mess, which Sage shouldn't > > duplicate. But arithmetic on lists isn't confusing. > > Agreed. We definitely didn't duplicate that lack of structure in Sage. > > > > > FWIW > > > > Robert Dodier > > > > > > > > > > > -- > William Stein > Associate Professor of Mathematics > University of Washington > http://wstein.org > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
