Thread: postfix vs prefix operators

Greetings all. I have what may seem to be a simple question on C++ that I would really like to know the answer to. Years ago I was attending the Software Developers expo in San Francisco, specifically a lecture by Dan Saks (C++ guru). Mr. Saks made an interesting observation that I would like to know the "why" of. Basically he said that using the prefix operator was somehow more efficient than the postfix when incrementing or decrementing numeric variables. Can anyone explain why:

++X;

Is any more efficient/faster/better than:
X++;

??? I have always wondered about this....

Cheers
Jeff

More accurately, the prefix version will typically be no less efficient than the postfix version, and may be more efficient. The reason is that a typical implementation of the postfix version will involve a temporary to return, whereas the prefix version has no need for such a temporary.

Originally Posted by laserlight

More accurately, the prefix version will typically be no less efficient than the postfix version, and may be more efficient. The reason is that a typical implementation of the postfix version will involve a temporary to return, whereas the prefix version has no need for such a temporary.

@LL: Thank you SO much for the reply. This bears out what Dan Saks said in the lecture but he did not explain why and since the topic (metaprogramming) dominated the Q&A afterworlds I never got a chance to ask. For most folks this will make no difference but in the land of embedded coding every clock-cycle counts.


Thank you again,
Jeff