Repository navigation
Using the Matrix/Vector Constructor does not work as expected with Polynomial Rings #6643
Description
This issue might be more of a design decision than a bug report, however in my opinion it should work to be able to create a Matrix/Vector with a Polynomial Ring as the Ring from a list/Matrix/Vector. This is the issue I ran into and discussed with @ThomasBreuer
gap> r := PolynomialRing(GF(4), 1);
GF(2^2)[x_1]
gap> Matrix(IsPlistMatrixRep, r, [[Z(4)]]);
Error, the elements in <list> must lie in <basedomain>
Stack trace:
*[1] Error( "the elements in <list> must lie in <basedomain>" );
@ /home/peter/gap/gap/lib/matobjplist.gi:78
[2] MakeIsPlistVectorRep( basedomain, PlainListCopy( list ), true )
@ /home/peter/gap/gap/lib/matobjplist.gi:166
[3] method( req1, req2, req3 )
@ /home/peter/gap/gap/lib/methsel.g:231
[4] NewVector( filterVectors, basedomain, list[i] )
@ /home/peter/gap/gap/lib/matobjplist.gi:201
[5] method( req1, req2, req3, req4 )
@ /home/peter/gap/gap/lib/methsel.g:254
... at *stdin*:29
you can enter 'quit;' to quit to outer loop, or
you can enter 'return;' to continueand
gap> Vector(r, [Z(4)]);
Error, the elements in <list> must lie in <basedomain>
Stack trace:
*[1] Error( "the elements in <list> must lie in <basedomain>" );
@ /home/peter/gap/gap/lib/matobjplist.gi:78
[2] MakeIsPlistVectorRep( basedomain, PlainListCopy( list ), true )
@ /home/peter/gap/gap/lib/matobjplist.gi:166
[3] method( req1, req2, req3 )
@ /home/peter/gap/gap/lib/methsel.g:231
[4] NewVector( DefaultVectorRepForBaseDomain( R ), R, l )
@ /home/peter/gap/gap/lib/matobj.gi:209
<function "Vector method">( <arguments> )
called from read-eval loop at *stdin*:36
you can enter 'quit;' to quit to outer loop, or
you can enter 'return;' to continueThis issue is probably caused by the following.
gap> Z(4) in r;
falseI would argue that using the constructors Matrix/Vector as above should be allowed, as the following also works:
gap> One(r);
Z(2)^0
gap> One(r) * Z(4);
Z(2^2)
gap> One(r) * Z(4) in r;
true
gap> One(r) * Z(4) = Z(4);
falseHence it also works to multiply Matrices consisting of lists within lists with elements from the polynomial ring and so forth.
gap> a := [[Z(4)]]*One(r);
[ [ Z(2^2) ] ]
gap> Matrix(IsPlistMatrixRep, r, a);
<1x1-matrix over PolynomialRing( GF(2^2), ["x_1"] )>Creating the matrix object like this feels like a hack, I think using the constructor should be the inteded solution.
Activity