gap-packages / qpa

GAP package for quivers and path algebras
https://folk.ntnu.no/oyvinso/QPA/
GNU General Public License v2.0
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Problem computing Dimension and taking quotients for PathAlgebraModule's #23

Closed erich-9 closed 6 years ago

erich-9 commented 6 years ago

The following is taken from the file examples/examples_path_algebras.g:

F := GF(11);
Q := Quiver(["v","w", "x"],[["v","w","a"],["v","w","b"],
["w","x","c"]]);
A := PathAlgebra(F,Q);
P := RightProjectiveModule(A,[A.v,A.v,A.w]);
Dimension(P);
##################
p1 := Vectorize(P,[A.b*A.c,A.a*A.c,A.c]);
p2 := Vectorize(P,[A.a,A.b,A.w]);
2*p1 + p2;
S := SubAlgebraModule(P,[p1,p2]);
Dimension(S);
##################
p2^(A.c - A.w);
##################
p1 < p2;
##################
PS := P/S;

Each of the lines Dimension(P), Dimension(S), and PS := P/S result in the following error:

Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `NewBasis' on 2 arguments at /usr/lib/gap/lib/methsel2.g:250 called from
NewBasis( V, info.echelonbas ) at /usr/lib/gap/pkg/qpa-1.27/lib/projpathalgmodule.gi:806 called from
BasisOfDomain( V ) at /usr/lib/gap/pkg/qpa-1.27/lib/projpathalgmodule.gi:892 called from
x in V at /usr/lib/gap/pkg/qpa-1.27/lib/projpathalgmodule.gi:787 called from
func( elm ) at /usr/lib/gap/lib/coll.gi:1613 called from
ForAll( vectors, function ( x )
      return x in V;
  end ) at /usr/lib/gap/pkg/qpa-1.27/lib/projpathalgmodule.gi:787 called from
olexandr-konovalov commented 6 years ago

@sunnyquiver it may be nice to add the example from this issue to a test file, especially since the commit message says "Not much thought has gone into this fix, please use with caution" - just in case the problem may strike again.