Question

In C++ I understand that (++i) should return a reference to i because the need of concatenation of operators, but what I can’t figure out is:

Why (i++) should return i by value?

Can anyone please clarify.

Answer 1

++i can be written as

prefix_inc (this) {
   increase this by 1
   return this
}

Since the real i is returned, we can take reference of it. However, i++ looks like

postfix_inc (this) {
   set old_this = copy of this
   increase this by 1
   return old_this
}

as old_this is just a local variable, the reference of it is pointless after i++ is completed. So logically it should return an rvalue.