What's wrong with my usage of std.algorithm.map in this code example?

[Chris via Digitalmars-d-learn]

On Wednesday, 25 May 2016 at 13:27:28 UTC, Chris wrote:
> On Wednesday, 25 May 2016 at 12:08:20 UTC, Steven Schveighoffer 
> wrote:
>> On 5/25/16 6:24 AM, pineapple wrote:
>>> On Tuesday, 24 May 2016 at 20:18:34 UTC, Steven Schveighoffer 
>>> wrote:
>>>> Slice assignment from range to array is not supported.
>>>>
>>>> In your example, I'm curious why the efforts to specify the 
>>>> type? I
>>>> think it would work with just saying auto itemstrings = ...
>>>>
>>>
>>> I still get an error if I use auto instead.
>>
>> OK, I see the other issue now. map takes a range, whereas you 
>> are giving it a tuple.
>>
>> -Steve
>
> Why can the tuple be iterated with foreach, as in my quick fix, 
> and indexed with tuple[0..], but is not accepted as a range? 
> What are the differences? Is there a way to rangify a tuple?

I should add : a homogeneous tuple, e.g. Tuple!(int, int, int);