Improvements to std.typecons.Nullable

[monarch_dodra]

On Tuesday, 8 October 2013 at 19:04:33 UTC, BLM768 wrote:
> I've been working on a project that makes relatively heavy use 
> of nullable values. I've been using std.typecons.Nullable, and 
> it mostly works well, but there are some improvements that 
> could be made to the implementation:
>
> * A toString() method (needed to fix bug #10915)
> * An opEquals for comparisons with the type that the Nullable 
> wraps
>   * Currently, comparing a null Nullable!T with a T produces an 
> error,
>     but it makes more sense to just return false.

OK, so that's two functions already. What about opCmp? What about 
toHash?

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.

> On Tue, 08 Oct 2013 22:55:34 +0200
> "monarch_dodra" <monarchdodra at gmail.com> wrote:
> > 
> > A Nullable!T isn't a T. It's a T handler.
> 
> I see that as an (unavoidable) implementation detail.

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.

> Personally, I find Nullable's "alias this" functionality to be a
wonderful convenience. FWIW.

I draw the line when convenience gets in the way of my programs 
not crashing.