opCaret to complement opDollar when specifying slices

[Steven Schveighoffer]

On Mon, 04 Jun 2012 17:23:57 -0400, Xinok <xinok at live.com> wrote:

> On Saturday, 2 June 2012 at 11:49:17 UTC, Dario Schiavon wrote:
>> Hi,
>>
>> I just read some old threads about opDollar and the wish to have it  
>> work for non zero-based arrays, arrays with gaps, associative arrays  
>> with non-numerical indices, and so on. It was suggested to define  
>> opDollar as the end of the array rather than the length (and perhaps  
>> rename opDollar to opEnd to reflect this interpretation), so that  
>> collection[someIndex .. $] would consistently refer to a slice from  
>> someIndex to the end of the collection (of course the keys must have a  
>> defined ordering for it to make sense).
>>
>> I'm just thinking, if we want to generalize slices for those cases,  
>> shouldn't we have a symmetrical operator for the first element of the  
>> array? Since the $ sign was evidently chosen to parallel the regexp  
>> syntax, why don't we add ^ to refer to the first element? This way,  
>> collection[^ .. $] would slice the entire collection, just like  
>> collection[].
>>
>> Until now, ^ is only used as a binary operator, so this addition  
>> shouldn't lead to ambiguous syntax. It surely wouldn't be used as often  
>> as the opDollar, so I understand if you oppose the idea, but it would  
>> at least make the language a little more "complete".
>
> The problem I see with this, it would be a larger burden when writing  
> generic code. Libraries would have to be written to compensate for those  
> containers. I'd prefer that all containers are simply zero-based, unless  
> there's a need for negative indices (i.e. pointers). I think  
> random-access ranges may be intended to be zero-based as well.

caret would have to map to 0 for slices and containers who already have a  
notion of first element being zero.

This would not be hard.  And in fact, would make generic code *easier*.   
Right now, you have to special case containers who support slicing but do  
not start on 0.  The only one I know of at this point is Red Black Tree.

-Steve