Questions about the slice operator

[Simen Kjærås]

On Wed, 04 Apr 2012 12:06:33 +0200, Jacob Carlborg <doob at me.com> wrote:

> On 2012-04-04 04:11, Jonathan M Davis wrote:
>
>> foreach(i; 0 .. 5)
>>
>> is more efficient only because it has _nothing_ to do with arrays.  
>> Generalizing
>> the syntax wouldn't help at all, and if it were generalized, it would  
>> arguably
>> have to be consistent in all of its uses, in which case
>>
>> foreach(i; 0 .. 5)
>>
>> would become identical to
>>
>> foreach(i; [0, 1, 2, 3, 4])
>>
>> and therefore less efficient. Generalizing .. just doesn't make sense.
>
> Why couldn't the .. syntax be syntax sugar for some kind of library  
> implement range type, just as what is done with associative arrays.
>
> We could implement a new library type, named "range". Looking something  
> like this:
>
> struct range
> {
>      size_t start;
>      size_t end;
>      // implement the range interface or opApply
> }
>
> range r = 1 .. 5;
>
> The above line would be syntax sugar for:
>
> range r = range(1, 5);
>
> void foo (range r)
> {
>      foreach (e ; r) {}
> }
>
> foo(r);
>
> This could then be taken advantage of in other parts of the language:
>
> class A
> {
>      int opSlice (range r); // new syntax
>      int opSlice (size_t start, size_t end); // old syntax
> }
>
> I think this would be completely backwards compatible as well.
>

And what do we do with 3..$?