On Wednesday, 9 October 2013 at 06:48:31 UTC, monarch_dodra wrote:
OK, so that's two functions already. What about opCmp? What
about toHash?
Since ordered comparisons make no sense with null values, opCmp
would need to throw an exception when working with null values
anyway. That's exactly what it does right now. I've considered
the other operators, and the same logic seems to apply to them.
As for toHash, that needs to be overloaded whenever opEquals is.
That's true for all types.
What if T is a range? Then "Nullable!T.empty" should return
true if the Nullable is empty. IF we don't, we'll get a crash
in foreach.
It does. Null is not an "empty" range; it's the _absence_ of a
range. They are not the same concept, and a null range _cannot_
be empty because the range does not exist. Therefore, it's a
logic error and should throw an exception.
If your range were class-based, you'd have exactly the same
issue, except that instead of getting an exception, you'd get a
segfault.
On Tue, 08 Oct 2013 22:55:34 +0200
"monarch_dodra" <[email protected]> wrote:
Is it though? C++ has done without it, and is still doing
without it. It has "implicit build from" which every one says
is mostly an abomination. Then here we are, bashing on their
implicit constructors, yet using "implicit cast to" O_o.
A major part of the problem in C++ stems from the existence of
two different forms of implicit conversion: the overloaded cast
operator and copy-constructors. D does not allow implicit
conversions with the latter, and it only allows implicit
conversion to one type with the former, which is considered
acceptable according to every C++ book I've read.
I draw the line when convenience gets in the way of my programs
not crashing.
Whether you have the "alias this" or not, if you try to get a T
out of a null Nullable!T, your program will throw an exception.
Leaving out the "alias this" would serve only as a reminder to
check for null, not as a solution to logic errors. When dealing
with a Nullable!T, just like when dealing with a nullable object
reference or a nullable pointer, you have to account for the null
state.
