Hi John!
On Oct 6, 9:30 am, John Cremona <[email protected]> wrote:
> A second point: if Simon is right then whenever a dense matrix is
> compared to a sparse one, the sparse one is first converted to a dense
> equivalent. That does not look very efficient to me, though it is
> true that when both are of size mxn then all m*n entries of the dense
> one might need to be looked at.
I was slightly mistaken: There is no _cmp_ with single underscores.
In sage.structure.element, you will find the following comment.
####################################################################
# For a derived Cython class, you **must** put the following in
# your subclasses, in order for it to take advantage of the
# above generic comparison code. You must also define
# either _cmp_c_impl (if your subclass is totally ordered),
# _richcmp_c_impl (if your subclass is partially ordered), or both
# (if your class has both a total order and a partial order;
# then the total order will be available with cmp(), and the
partial
# order will be available with the relation operators; in this
case
# you must also define __cmp__ in your subclass).
# This is simply how Python works.
#
# For a *Python* class just define __cmp__ as always.
# But note that when this gets called you can assume that
# both inputs have identical parents.
#
# If your __cmp__ methods are not getting called, verify that the
# canonical_coercion(x,y) is not throwing errors.
#
####################################################################
So, the things are a little complicated, in the sense that the
behaviour for Cython and Python is different.
Moreover, if __cmp__ is implemented then it is called *after*
coercion.
Cheers,
Simon
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