Let G be a semisimple
simply connected affine algebraic group over an algebraically closed field k of
characteristic zero, let A(G) be the k-algebra of regular functions of G, and let C(G)
be the subalgebra consisting of class functions. We explain how Lusztig’s work on
canonical bases affords a constructive proof of the fact, due to Richardson, that A(G)
is a free C(G)-module.