Steven Schveighoffer wrote:
On Thu, 03 Sep 2009 10:40:13 -0400, Leandro Lucarella <[email protected]>
wrote:
Andrei Alexandrescu, el 2 de septiembre a las 14:39 me escribiste:
I plan to add a Nullable struct to Phobos (akin to C#'s Nullable,
Boost's Optional).
Apparently a good design is to define Optional!T with a minimum of
member functions (ideally none) and have it use the "alias this"
feature to masquerade as a
T. That way Optional!T looks and feels much like a T, except that it
supports a function
bool isNull(T)(Optional!T value);
Am I on the right track? If so, what is the name you'd prefer for
this artifact?
Maybe this is a very silly question, but what is exactly the difference
between Optional!T o/isNull(o) and T* o/o is null?
The difference is you don't have to store the T somewhere else. That
is, an Optional!T contains both the value if it is not null AND whether
it is null or not. With a T*, the value is stored elsewhere, and you
may have aliasing problems.
-Steve
Oh, that I forgot and is essential! A closer question is what's the
difference between OptionalRef!T and T*. That difference is smaller
because OptionalRef!T actually stores exactly a T* inside.
Andrei
