Error with AlmostSplitSequenceInPerpT?

[Nakayamaalgebra]

Hi, the following example for AlmostSplitSequenceInPerpT seems to lead to an error:

A:=NakayamaAlgebra([2,3],GF(3));projA:=IndecProjectiveModules(A);injA:=IndecInjectiveModules(A); CoRegA:=DirectSumOfQPAModules(IndecInjectiveModules(A));prinj:=Filtered(injA,x->IsProjectiveModule(x)=true);U:=DirectSumOfQPAModules(prinj);TT:=NthSyzygy(CoRegA,1);T:=DirectSumOfQPAModules([U,TT]); f:=AlmostSplitSequenceInPerpT(T,projA[1]);

Thanks for any help.

[sunnyquiver]

There is no almost split (exact) sequence ending in an indecomposable projective module. The second argument in the above example is an indecomposable projective module, so that there is no almost split sequence ending in that module. The function did not return the proper output for this case. Now the function will return fail if the second argument is a projective module. The projective objects in ^\perp T are exactly the projective modules, which implies that there cannot be an almost split sequence in \perp T ending there. The function and the documentation have been updated with this in mind.

Thank you very much for spotting this bug. The QPA-team.