William Stein 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.) > > 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.
Maybe for python ints, but surely we can make Sage Integers work without raising exceptions, as illustrated on the top portion of http://sagenb.org/home/pub/699/ ? (Of course, keeping in mind that the "1" in the examples above is likely to be a Sage Integer, not a python int, so we could add (if desired) functions to add/radd the Integer to a list.) Personally, I much prefer list comprehension for a case like this. In fact, I just finished writing an entire reply and example on the assumption that [1,2,3]+4 would yield [1,2,3,4], as that was what I expected from the current python behavior of [1,2,3]+[4] (i.e., list addition is list concatenation!) Then I realized the proposal was something different, so I had to change everything. Also, someone could define a +eadd+ operator that would be like the +. operator in Matlab. With the code from http://trac.sagemath.org/sage_trac/ticket/6245 (appropriately modified for "+" precedence), you could do something like the bottom half of http://sagenb.org/home/pub/699/, which gives: sage: [1,2,3] +eadd+ 4 [5, 6, 7] sage: 1 +eadd+ [2,3,4] [3, 4, 5] Thanks, Jason --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
