Rebinding semantics for the assignment of initialized optional references has been chosen to provide consistency among initialization states even at
Greetings, boost::optional<T &> seems to be implemented in terms of a boolean flag and an aligned_storage. Wouldn’t it make more sense to make boost::optional<T &> a thin wrapper over T*? This would save a couple of bytes, speed up get_ptr by a couple of ticks, and perhaps reduce compilation times. Also, from the documentation[1]: the expense of lack of consistency with the semantics of bare C++ references. It is true that optional<U> strives to behave as much as possible as U does whenever it is initialized; but in the case when U is T&, doing so would result in inconsistent behavior w.r.t to the lvalue initialization state. optional<U> does not have the semantics of U, but rather those of U*. That explains the assignment semantics perfectly well: int a = 1; int b = 2; int& ra = a; int& rb = b; int* pa = &a; int* pb = &b; boost::optional<int &> oa(ra); boost::optional<int &> ob(rb); ra = rb; // assigns b to a pa = pb; // rebinds pa to b oa = ob; // rebinds oa to b -- [1] http://tinyurl.com/55s8f7 -- WBR Roman.