Hi,
In Sage 5.0, I'm getting the following strange behavior with sparse
matrices. As they should, the following two methods produce the same
cyclic permutation matrix:
sage> A = matrix(QQ,5,{(j,mod(j+1,5)):1 for j in range(5)}); A
[0 1 0 0 0]
[0 0 1 0 0]
[0 0 0 1 0]
[0 0 0 0 1]
[1 0 0 0 0]
sage> B = matrix(QQ,5,{(0, 1): 1, (1, 2): 1, (3, 4): 1, (2, 3): 1, (4,
0): 1}); B
[0 1 0 0 0]
[0 0 1 0 0]
[0 0 0 1 0]
[0 0 0 0 1]
[1 0 0 0 0]
sage: A == B
True
However, when I replace QQ with a number field (or CC,CDF, CLF, etc),
the first way displays incorrectly even though they are still equal:
sage: A = matrix(QuadraticField(2),5,{(j,mod(j+1,5)):1 for j in
range(5)}); A
[1 1 1 1 1]
[0 0 0 0 0]
[0 0 0 0 0]
[0 0 0 0 0]
[0 0 0 0 0]
sage: B = matrix(QuadraticField(2),5,{(0, 1): 1, (1, 2): 1, (3, 4): 1,
(2, 3): 1, (4, 0): 1}); B
[0 1 0 0 0]
[0 0 1 0 0]
[0 0 0 1 0]
[0 0 0 0 1]
[1 0 0 0 0]
sage> A == B
True
So is this a bug, or is there some subtle aspect of the set { ... }
constuction that I'm misusing?
Thanks,
Jon
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