A finite dimensional F-algebra A is always a finite dimensional
F-vector space.
Thus in GAP, an algebra is a vector space (see IsVectorSpace),
and vector space functions such as Base and Dimension are applicable
to algebras.
gap> a:= UnitalAlgebra( Rationals, [ [ [ 1, 0 ], [ 0, 0 ] ] ] );
UnitalAlgebra( Rationals, [ [ [ 1, 0 ], [ 0, 0 ] ] ] )
gap> Dimension( a );
2
gap> Base( a );
[ [ [ 1, 0 ], [ 0, 1 ] ], [ [ 0, 0 ], [ 0, 1 ] ] ]
The vector space structure is used also by the set theoretic functions.
GAP 3.4.4