Range of uncopyable elements

[Jerry via Digitalmars-d-learn]

On Thursday, 8 December 2016 at 16:48:07 UTC, H. S. Teoh wrote:
> On Thu, Dec 08, 2016 at 04:35:02PM +0000, Jerry via 
> Digitalmars-d-learn wrote:
>> The problem is with how isInputRange is defined, requires that 
>> front be copyable.
>> 
>> auto h = r.front; // can get the front of the range
>> 
>> https://github.com/dlang/phobos/blob/v2.072.1/std/range/primitives.d#L168
>> 
>> It doesn't take into consideration that front exists and that 
>> it's a reference to a struct that can't be copied. There was a 
>> discussion a while back to change it but it seems nothing came 
>> of it.
>
> A possible workaround, which is somewhat ugly but should work, 
> is to have the range return pointers to the elements instead of 
> the elements themselves. For the most part, this should be 
> mostly transparent because the . operator automatically 
> dereferences.
>
>
> T

It's not something that you should have to workaround, 
isInputRange is not defined properly and should be fixed. You end 
up complicating your code for no reason other than isInputRange 
is poorly defined.