On 1/26/12 8:21 PM, Tom Boothby wrote:
On Thu, Jan 26, 2012 at 5:15 PM, David Roe<r...@math.harvard.edu> wrote:
Another issue: do we allow [1..10; 10..20]?
We probably shouldn't go to extra effort to support it.
I can't seem to construct
matrices with matrix entries (this is not absurd) -- but should the
preparser grok it? [[1..10; 10..20] ; [2..12; 14..24]]
Yes, for sure. And [[1..10; 10..20].det() ; [2..12; 14..24].det()]
I'm not quite clear how these are square matrices (or even how the
rows have the same length). What does [1..10; 10..20] translate to?
They aren't square... and worse, [1..10; 10..20] doesn't make sense
since the top row has 9 entries whereas the bottom has 10. We're
being sloppy for the sake of conversation. I tend to think that we
should support ellipses, though I admit it's a corner case of limited
utility.
[0..2; 10..12] -> [[0,1,2],[10,11,12]]
Two comments:
1. If [0..2, 10..12] works, I think matrix([[0..2],[10..12]]) should
work. Notice, with the current patch:
sage: matrix([[0..2],[10..12]])
[ 0 1 2]
[10 11 12]
sage: [0..2;10..12]
------------------------------------------------------------
File "<ipython console>", line 1
(ellipsis_range(Integer(0),Ellipsis,Integer(2);Integer(10),Ellipsis,Integer(12)))
^
SyntaxError: invalid syntax
sage: preparse('[0..1;3..4]')
'(ellipsis_range(Integer(0),Ellipsis,Integer(1);Integer(3),Ellipsis,Integer(4)))'
So maybe we just need to switch the order of preparsing? Indeed, moving
the matrix preparsing call ahead of the ellipsis call gives:
sage: preparse('[0..2; 3..5]')
'matrix([(ellipsis_range(Integer(0),Ellipsis,Integer(2))),(ellipsis_range(
Integer(3),Ellipsis,Integer(5)))])'
sage: [0..2; 3..5]
[0 1 2]
[3 4 5]
2. Matlab supports such notation (except they use a colon to give a
range, like 0:10 for [0..10] and 0:2:10 for [0..10,step=2]). It would
be nice if we supported it as well. With the above change, we also get
that for free:
sage: [0..10,step=2; 1..11,step=2]
[ 0 2 4 6 8 10]
[ 1 3 5 7 9 11]
sage: [0,2,..,10; 2,4,..,12]
[ 0 2 4 6 8 10]
[ 2 4 6 8 10 12]
I'm not sure if there is a problem with moving the matrix parsing up
that early in the preparsing stage, though.
Jason
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