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An element method for vector_space_homspace.py #16940

Open ghost opened 10 years ago

ghost commented 10 years ago

We implement an an_element method for Hom spaces of vector spaces which returns a somewhat typical element in the space (instead of the boring 0 matrix!)

CC: @nthiery

Component: categories

Author: Kamalakshya Mahatab, Kannappan Sampath

Branch/Commit: public/kamalakshya/an_element @ ea7fff3

Issue created by migration from https://trac.sagemath.org/ticket/16940

videlec commented 9 years ago
comment:2

Hello,

Actually I think that this is a bug

sage: V1 = GF(2)**3
sage: V2 = GF(7)**5
sage: Hom(V1,V2)
Set of Morphisms (Linear Transformations)
from 
  Vector space of dimension 3 over Finite Field of size 2
to
  Vector space of dimension 5 over Finite Field of size 7
sage: _.category()
Category of homsets of modules with basis over (finite fields
and subquotients of monoids and quotients of semigroups)

Don't you?

I would either open another ticket or solve it here (at the level of FreeModuleHomspace). In your _an_element_ you should not worry about the EmptySetError being raised. The homset between free modules (over the same base ring) always contain zero and so is never empty!

Vincent

videlec commented 9 years ago
comment:3

See #18309 for the issue about Hom.