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

You're asking about C specifically, but C++ builds upon this as well:

Most pointer arithmetic naturally generalizes to the Forward Iterator concept. Walking through memory with *p++ can be used for any sequenced container (linked list, skip list, vector, binary tree, B tree, etc), thanks to operator overloading.

Answer 2

iterating through a 2-dimensional array where the position of a datum does not really matter
if you dont use pointers, you would have to keep track of two subscripts
with pointers, you could point to the top of your array, and with a single loop, zip through the whole thing

Answer 3

If you were using an old compiler, or some kind of specialist embedded systems compiler, there might be slight performance differences, but most modern compilers would probably optimize these (tiny) differences out.

The following article might be something you could draw on - depends on the level of your students:

http://geeks.netindonesia.net/blogs/risman/archive/2007/06/25/Pointer-Arithmetic-and-Array-Indexing.aspx