template bool SoftSurfaceEqual::operator()(S<Axis::x> const&, \
S<Axis::x> const&) const; \
template bool SoftSurfaceEqual::operator()(S<Axis::y> const&, \
S<Axis::y> const&) const; \
template bool SoftSurfaceEqual::operator()(S<Axis::z> const&, \
S<Axis::z> const&) const