Hi there,
I found this:
sage: c = CartanType([["A",2]])
sage: c.is_irreducible()
False
And it has further nasty consequences:
sage: c.cartan_matrix()
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/home/jesus/<ipython console> in <module>()
/home/jesus/trabajo/sage-5.4-linux-32bit-ubuntu_12.04.1_lts-i686-Linux/local/lib/python2.7/site-packages/sage/combinat/root_system/type_reducible.pyc
in cartan_matrix(self, subdivide)
229 [ 0 0 -2 2]
230 """
--> 231 return block_diagonal_matrix([t.cartan_matrix() for t in
self._types], subdivide=subdivide)
232
233 def dynkin_diagram(self):
/home/jesus/trabajo/sage-5.4-linux-32bit-ubuntu_12.04.1_lts-i686-Linux/local/lib/python2.7/site-packages/sage/matrix/constructor.pyc
in block_diagonal_matrix(*sub_matrices, **kwds)
2654 for i in range(n):
2655 entries[n*i+i] = sub_matrices[i]
-> 2656 return block_matrix(n, n, entries, **kwds)
2657
2658 def jordan_block(eigenvalue, size, sparse=False):
/home/jesus/trabajo/sage-5.4-linux-32bit-ubuntu_12.04.1_lts-i686-Linux/local/lib/python2.7/site-packages/sage/matrix/constructor.pyc
in block_matrix(*args, **kwds)
2617 if subdivide:
2618 big.subdivide(running_total(row_heights[:-1]),
-> 2619 running_total(col_widths[:-1]))
2620
2621 return big
/home/jesus/trabajo/sage-5.4-linux-32bit-ubuntu_12.04.1_lts-i686-Linux/local/lib/python2.7/site-packages/sage/matrix/matrix2.so
in sage.matrix.matrix2.Matrix.subdivide (sage/matrix/matrix2.c:34031)()
/home/jesus/trabajo/sage-5.4-linux-32bit-ubuntu_12.04.1_lts-i686-Linux/local/lib/python2.7/site-packages/sage/matrix/matrix0.so
in sage.matrix.matrix0.Matrix.check_mutability
(sage/matrix/matrix0.c:4215)()
ValueError: matrix is immutable; please change a copy instead (i.e., use
copy(M) to change a copy of M).
I have written a short 2-lines patch that I think could be reviewed in 5
minutes. May I open a ticket?
Cheers,
Jesús Torrado
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