  Motivated by recent efforts to analyze corrections to Weinberg's relations
for the scattering length and effective range in the presence of a
near-threshold bound state, we play around with an instructive toy model for
non-relativistic scattering in a central potential. The model allows to
interpolate between bound-state configurations of high "compositeness", where
the wave function is spread over a wide region beyond the range of the
interaction, and compact configurations of high "elementariness", where the
wave function is confined to a small region around the center of the potential.
