On Fri, Mar 7, 2008 at 10:57 AM, William Stein <[EMAIL PROTECTED]> wrote:
>
> On Fri, Mar 7, 2008 at 7:35 AM, David Joyner <[EMAIL PROTECTED]> wrote:
> >
> > Hi:
> > Is there a reason why Set only applies to hashable elements?
>
> Set is implemented using the Python language's builtin set type, which
> in turn requires that elements by hashable.
Since SAGE's uniq also required the elements to be hashable, I wonder
if anyone things that the above routine should replace it?
>
>
> > It is faster than
> > http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52560
> > at removing duplicates from a list (which is what I need) but does not
> > apply, for example, to lists of matrices:
>
> FYI -- If you make the matrices immutable then you can hash them.
Thanks.
>
>
> >
> >
> > sage: MS = MatrixSpace(GF(7),2,2)
> > sage: A = MS.identity_matrix()
> > sage: B = 2*A
> > sage: L = [A,A,B]
> > sage: Set(L)
> >
> ---
> > Traceback (most recent call
> last)
> >
> > /mnt/drive_hda1/sagefiles/sage-2.10.3.rc2/ in ()
> >
> >
> /home/wdj/wdj/sagefiles/sage-2.10.3.rc2/local/lib/python2.5/site-packages/sage/sets/set.py
> > in Set(X)
> > 78 raise TypeError, "Element has no defined underlying set"
> > 79 elif isinstance(X, (list, tuple, set, frozenset)):
> > ---> 80 return Set_object_enumerated(frozenset(X))
> > 81 try:
> > 82 if X.is_finite():
> >
> > /mnt/drive_hda1/sagefiles/sage-2.10.3.rc2/matrix_modn_dense.pyx in
> > sage.matrix.matrix_modn_dense.Matrix_modn_dense.__hash__()
> >
> > /mnt/drive_hda1/sagefiles/sage-2.10.3.rc2/matrix_dense.pyx in
> > sage.matrix.matrix_dense.Matrix_dense._hash()
> >
> > : mutable matrices are unhashable
> >
> >
> > - David Joyner
> >
> > >
> >
>
>
>
> --
> William Stein
> Associate Professor of Mathematics
> University of Washington
> http://wstein.org
>
> >
>
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