ASKSAGE: Sage Q&A Forum - Individual question feedhttp://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Tue, 30 Oct 2018 15:44:39 -0500How do I define a homomorphism of a graded commutative algebra?http://ask.sagemath.org/question/44109/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/ I am working on implementing morphisms of graded commutative algebras. I have two graded commutative algebra, A with generators <w,x> and B with generators <y,z> . I define H the set of homomorphisms from A to B. Then, I want to define the homomorphisms f such that f(w)=y and f(x)=0 but I get an error:
sage: H = Hom(A,B)
sage: H([y,0])
TypeError: images do not define a valid homomorphism
Mon, 29 Oct 2018 04:26:05 -0500http://ask.sagemath.org/question/44109/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/Comment by rburing for <p>I am working on implementing morphisms of graded commutative algebras. I have two graded commutative algebra, A with generators <w,x> and B with generators <y,z> . I define H the set of homomorphisms from A to B. Then, I want to define the homomorphisms f such that f(w)=y and f(x)=0 but I get an error:</p>
<p>sage: H = Hom(A,B)
sage: H([y,0])</p>
<p>TypeError: images do not define a valid homomorphism</p>
http://ask.sagemath.org/question/44109/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/?comment=44116#post-id-44116Are you using the latest version of SageMath? In 8.4 some bugs just like this were fixed.Mon, 29 Oct 2018 13:02:02 -0500http://ask.sagemath.org/question/44109/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/?comment=44116#post-id-44116Comment by dan_fulea for <p>I am working on implementing morphisms of graded commutative algebras. I have two graded commutative algebra, A with generators <w,x> and B with generators <y,z> . I define H the set of homomorphisms from A to B. Then, I want to define the homomorphisms f such that f(w)=y and f(x)=0 but I get an error:</p>
<p>sage: H = Hom(A,B)
sage: H([y,0])</p>
<p>TypeError: images do not define a valid homomorphism</p>
http://ask.sagemath.org/question/44109/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/?comment=44113#post-id-44113Please insert the code for $A,B$, so that we can reproduce the situation and the errors. Please use that button with `101` over `010` (after B, and I, and the Link buttons...) to format properly the code. (Copy+paste the code, mark it, press that button or the combination Control+K on the selection.)Mon, 29 Oct 2018 08:41:29 -0500http://ask.sagemath.org/question/44109/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/?comment=44113#post-id-44113Answer by John Palmieri for <p>I am working on implementing morphisms of graded commutative algebras. I have two graded commutative algebra, A with generators <w,x> and B with generators <y,z> . I define H the set of homomorphisms from A to B. Then, I want to define the homomorphisms f such that f(w)=y and f(x)=0 but I get an error:</p>
<p>sage: H = Hom(A,B)
sage: H([y,0])</p>
<p>TypeError: images do not define a valid homomorphism</p>
http://ask.sagemath.org/question/44109/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/?answer=44121#post-id-44121See https://ask.sagemath.org/question/42202/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/ for an almost identical question. As @rburing points out, this has been fixed in recent versions of Sage: see https://trac.sagemath.org/ticket/26027.Tue, 30 Oct 2018 15:44:39 -0500http://ask.sagemath.org/question/44109/how-do-i-define-a-homomorphism-of-a-graded-commutative-algebra/?answer=44121#post-id-44121