On Wednesday, 15 August 2012 at 00:32:43 UTC, Walter Bright wrote:
On 8/14/2012 3:57 PM, Mehrdad wrote:
I guess they aren't really default constructors, then <g>.
I say potayto, you say potahto... :P
So what happens when you allocate an array of them?
For arrays, they're called automatically.
Well, OK, that's a bit of a simplification.
It's what happens from the user perspective, not the compiler's
(or runtime's).
Here's the full story.
And please read it carefully, since I'm __not__ saying D should
adopt what C# does word for word!
In C#:
- You can define a custom default constructor for classes, but
not structs.
- Structs _always_ have a zero-initializing default
(no-parameter) constructor.
- Therefore, there is no such thing as "copy construction"; it's
bitwise-copied.
- Ctors for _structs_ MUST initialize every field (or call the
default ctor)
- Ctors for _classes_ don't have this restriction.
- Since initialization is "Cheap", the runtime _always_ does it,
for _security_.
- The above^ is IRRELEVANT to the compiler!
* It enforces initialization where it can.
* It explicitly tells the runtime to auto-initialize when it
can't.
-- You can ONLY take the address of a variable in unsafe{}
blocks.
-- This implies you know what you're doing, so it's not a
problem.
What D would do _ideally_, IMO:
1. Keep the ability to define default (no-args) and postblit
constructors.
2. _Always_ force the programmer to initialize _all_ variables
explicitly.
* No, this is NOT what C++ does.
* Yes, it is tested & DOES work well in practice. But NOT in
the C++ mindset.
* If the programmer _needs_ vars to be uninitialized, he can
say = void.
* If the programmer wants NaNs, he can just say = T.init.
Bingo.
It should work pretty darn well, if you actually give it a try.
(Don't believe me? Put it behind a compiler switch, and see how
many people start using it, and how many of them [don't] complain
about it!)
D could take a similar approach.
It could, but default construction is better (!).
Well, that's so convincing, I'm left speechless!
