What are convincing examples where pointer arithmetic is preferable to array subscripting?

Question

I\'m preparing some slides for an introductory C class, and I\'m trying to present good examples (and motivation) for using pointer arithmetic over array subscripting.

Answer 1

Something fun I hope you never have to deal with: pointers can alias, whereas arrays cannot. Aliasing can cause all sorts of non-ideal code generation, the most common of which is using a pointer as an out parameter to another function. Basically, the compiler cannot assume that the pointer used by the function doesn't alias itself or anything else in that stack frame, so it has to reload the value from the pointer every time it's used. Or rather, to be safe it does.