Option!T

[monarch_dodra]

On Tuesday, 10 December 2013 at 19:26:27 UTC, Andrei Alexandrescu 
wrote:
> On 12/10/13 10:59 AM, monarch_dodra wrote:
>> On Tuesday, 10 December 2013 at 17:28:26 UTC, Andrei 
>> Alexandrescu
>> wrote:
>>> We have only(x) 
>>> (http://dlang.org/phobos/std_range.html#.only) to be a
>>> collection of exactly one value, but not a type for "a value 
>>> of type T
>>> or nothing at all"
>>
>> Option is being upgraded to handle an arbitrary (but compile 
>> time
>> known) amount of values:
>> https://github.com/D-Programming-Language/phobos/pull/1743
>
> Interesting! There is the problem one can't represent "no 
> element of type T" and "one element of type T" with the same 
> type.

Hum... True. Well... "T[]", I guess :)

> There's also the unrelated issue that the result of the 
> proposed only() is passed around by value, even after it has 
> been partially discarded.

Yes, but that also means than slicing doesn't escape a references 
to temporaries about the go out of scope: It carries around its 
payload.

But, I see no reason not to implement an "Option": The way I see 
it, it "completes" our range package. Each tool has its pros and 
cons.

I'm also working on a "staticArray", that can create static 
arrays on the fly. That too can also be used just like "only", 
but it does not carry arround its data by value. I'll finish the 
ER, and the pull, and you'll get more details. It seems like very 
useful stuff to me anyways.