Corporal punishment has no demonstrable positive effects. In the short-term, the child might be fearful or obedient, but in the long-term, there is no consistent improvement in behavior.
discipline
Friend or parent?
Parents can be a friend for their children. These two concepts mix together quite nicely when executed in good faith.
Discipline does not equal punishment
The intrinsic problem with equating discipline with punishment is a misunderstanding of the meaning of discipline. The word discipline comes from a root word meaning to teach or instruct.