On Sun, Aug 2, 2009 at 9:13 AM, Robert Dodier<[email protected]> 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.)
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. > > 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 [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
