Well, the main point of the item about post-increment operator spacing is that there should
not be a space between the identifier and the operator - this is just tradition, as we're all so used to seeing this without a space that it would annoy a lot of us to see it otherwise. If you're asking why is there a space between the operator and the semicolon, that part isn't actually required. In Coop style you see a lot of semicolons with spaces in front of them because they come after identifiers, and Coop style requires space around identifiers except for the exceptions noted. Of course ++ and -- aren't actually identifiers, so no space is actually required between ++ and ;, or -- and ;. But if you want to put one there you're welcome to do so, simply because the Coop tends to put in a lot of extra spaces anyway in places normal people would never put them.
So:
<code><pre>i ++; // bad
i++; // good
i ++ ; // bad
i++ ; // good</pre></code>
[This message has been edited by Jim Yingst (edited March 16, 2001).]