  In this paper, we deal with the boundary controllability of a one-dimensional
degenerate and singular wave equation with degeneracy and singularity occurring
at the boundary of the spatial domain. Exact boundary controllability is proved
in the range of subcritical/critical potentials and for sufficiently large
time, through a boundary controller acting away from the degenerate/singular
point. By duality argument, we reduce the problem to an observability estimate
for the corresponding adjoint system, which is proved by means of the
multiplier method and a new special Hardy-type inequality.
