#14537: Composition of morphisms
------------------------------------------------+---------------------------
Reporter: tfeulner | Owner: nthiery
Type: defect | Status:
positive_review
Priority: major | Milestone: sage-5.11
Component: categories | Resolution:
Keywords: composition, morphisms, sd48 | Work issues:
Report Upstream: N/A | Reviewers: Volker Braun
Authors: Thomas Feulner | Merged in:
Dependencies: | Stopgaps:
------------------------------------------------+---------------------------
Description changed by nthiery:
Old description:
> The following code leads to a TypeError:
> {{{
> sage: F.<a> = GF(4)
> sage: f = F.Hom(F).identity()
> sage: g = F.hom([a])
> sage: h = (g*f)
> sage: f*h
> ...
> TypeError: right (=Composite map:
> From: Finite Field in a of size 2^2
> To: Finite Field in a of size 2^2
> Defn: Identity endomorphism of Finite Field in a of size 2^2
> then
> Ring endomorphism of Finite Field in a of size 2^2
> Defn: a |--> a) must be a morphism to multiply it by Identity
> endomorphism of Finite Field in a of size 2^2
> }}}
>
> The problem is solved by relaxing the type checking in the multiplication
> procedure.
New description:
The following code leads to a TypeError:
{{{
sage: F.<a> = GF(4)
sage: f = F.Hom(F).identity()
sage: g = F.hom([a])
sage: h = (g*f)
sage: f*h
...
TypeError: right (=Composite map:
From: Finite Field in a of size 2^2
To: Finite Field in a of size 2^2
Defn: Identity endomorphism of Finite Field in a of size 2^2
then
Ring endomorphism of Finite Field in a of size 2^2
Defn: a |--> a) must be a morphism to multiply it by Identity
endomorphism of Finite Field in a of size 2^2
}}}
The problem is solved by relaxing the type checking in the multiplication
procedure to accept Maps and not only Morphisms
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14537#comment:4>
Sage <http://www.sagemath.org>
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