  In the basic representation of $U_q(\hat{sl}(2))$ realized via the algebra of
symmetric functions we compare the canonical basis with the basis of Macdonald
polynomials with $q=t^2$. We show that the Macdonald polynomials are invariant
with respect to the bar involution defined abstractly on the representations of
quantum groups. We also prove that the Macdonald scalar product coincides with
the abstract Kashiwara form. This implies, in particular, that the Macdonald
polynomials form an intermediate basis between the canonical basis and the dual
canonical basis, and the coefficients of the transition matrix are necessarily
bar invariant. We also discuss the positivity and integrality of these
coefficients. For level $k$, we expect a similar relation between the canonical
basis and Macdonald polynomials with $q^2=t^{k}.$
