Hi Florent, Robert,
On Mon, Oct 26, 2009 at 06:56:39PM +0100, Florent hivert wrote:
> I'm having trouble with coercion in sage 4.2...
> The following (reduced) example works with sage 4.1.2 and breaks with sage
> 4.2. Here is the error:
>
> File "<doctest __main__.example_0[2]>", line 1, in <module>
> bla = Essai(); bla###line 11:
> sage: bla = Essai(); bla
> File "/home/averell/.sage/tmp/wrapp.py", line 16, in __init__
> mor.register_as_coercion()
> File "morphism.pyx", line 116, in
> sage.categories.morphism.Morphism.register_as_coercion
> (sage/categories/morphism.c:2371)
> File "parent.pyx", line 1018, in
> sage.structure.parent.Parent.register_coercion (sage/structure/parent.c:8301)
> File "parent.pyx", line 1043, in
> sage.structure.parent.Parent.register_coercion (sage/structure/parent.c:8090)
> AssertionError: coercions must all be registered up before use
>
> Any help or suggestion ?
A quick note: #5598 (allow post-creation (pre-use) declaration of
coercions) went in Sage in 4.2. Before that, we were using in
Sage-Combinat a pure Python version without sanity checks.
I haven't thought out your example. But we have similar issues in a
couple of our categories/examples. Now the question is: are the checks
in register_as_coercion too rigid for practical use cases? Or should
we be somehow more lazy in those use cases?
Cheers,
Nicolas
> from sage.structure.parent import Parent
> from sage.rings.integer_ring import IntegerRing
> from sage.categories.homset import Hom
> class Essai(Parent):
> """
> TESTS::
>
> sage: bla = Essai(); bla
> <class 'wrapp.Essai'>
> """
> def __init__(self):
> Parent.__init__(self)
> mor = Hom(self, IntegerRing())(lambda z: 1)
> mor.register_as_coercion()
>
> Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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