Option!T

[Idan Arye]

On Tuesday, 10 December 2013 at 22:10:49 UTC, Jesse Phillips 
wrote:
> On Tuesday, 10 December 2013 at 17:28:26 UTC, Andrei 
> Alexandrescu wrote:
>> I talked to a programmer who knows Scala (among others) and he 
>> mentioned the usefulness of the Option type - a zero or one 
>> element collection (range in D terminology). Here's an article 
>> discussing it: 
>> http://danielwestheide.com/blog/2012/12/19/the-neophytes-guide-to-scala-part-5-the-option-type.html
>>
>> 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". Should we follow Scala's 
>> example and add it?
>>
>>
>> Andrei
>
> Having a easy way to return a single element range which may be 
> empty is probably a good idea. It could make a good change to 
> style, but I don't use Option in other languages. For that 
> reason I'm not sure Option range probably doesn't have the same 
> semantics as expected by users of other languages.

That's a good point. `Option` is usually used with pattern 
matching, so the value is used in a clause that is only executed 
if it has a 
value(http://en.wikipedia.org/wiki/Option_type#Examples). This 
can easily be implemented in D: 
https://gist.github.com/someboddy/7902770