MapFromIntersectionMatricesToCentralIdempotents

[johnbamberg]

There is a bug in “MapFromIntersectionMatricesToCentralIdempotents”, but I’m not sure the best way to fix it. If you have a non-commutative intersection algebra, and HasNumberOfCharacters(A) is false, then it passes to the “else” part. But then it asks for Length(Idem) and Idem is not known at this point.

cc:=HomogeneousCoherentConfiguration(10,10);
intalg:=IntersectionAlgebraOfHomogeneousCoherentConfiguration(cc);
MapFromIntersectionMatricesToCentralIdempotents(intalg);
Error, Variable: 'Idem' must have an assigned value in
  for i in [ 1 .. Length( Idem ) ] do
    if Conductor( F ) mod Conductor( DefaultFieldOfMatrix( Idem[i] ) ) = 0 then
        IM2 := List( IntersectionMatrices( A ), function ( x )
                return x * Idem[i];
            end );
        Add( IM2, IdentityMat( NumberOfClasses( A ) + 1 ) );
        IM2 := Set( IM2 );
        Alg := Algebra( F, IM2 );
        Append( Idem2, CentralIdempotentsOfAlgebra( Alg ) );
    else
        Add( Idem2, Idem[i] );
    fi;
od; at /Users/00044445/pkg/AssociationSchemes/gap/IntersectionAlgebraObject/Idempotents.gi\
:167 called from 
<function "MapFromIntersectionMatricesToCentralIdempotents for IsAssociationScheme">( <arg\
uments> )
 called from read-eval loop at *stdin*:681
type 'quit;' to quit to outer loop