Issue with forward ranges which are reference types

[Jesse Phillips]

On Tue, 16 Aug 2011 21:17:31 -0700, Mehrdad wrote:

> On 8/16/2011 9:05 PM, Jonathan M Davis wrote:
>> Sorry that this is long, but it's very important IMHO, and I don't know
>> how to make it much shorter and cover what it's supposed to cover.
>>
>> Okay. Your typical forward range is either an array a struct which is a
>> value type (that is, copying it creates an independent range which
>> points to the same elements and is not altered if the original range is
>> altered - the elements that it points to aren't copied of
>> course).<snip> Thoughts?
>>
>> - Jonathan M Davis
> Funny, I was also thinking about this recently.
> 
> The trouble is that that's not the only issue. There's also the issue
> with polymorphism -- i.e., InputRangeObject is pretty much *useless*
> right now because no function ever checks for it (AFAIK... am I wrong?).
> So if you pass a random-access range object as an InputRange, the callee
> will just assume it's an InputRange and would reject it. So you're
> forced to downcast every time, which is really tedious. Things don't
> "just work" anymore.

All of the range functions check for functionality, so if your random-
access range object contains, popFront, front, empty (which it is 
required to to be random-access range) then it will be accepted as an 
InputRange.

Considering your work I'm sure you know this so I'm probably 
misunderstanding what point your are making?