Ranges: is it ok if front is a data member?

[Jesse Phillips]

On Thursday, 12 December 2013 at 16:52:12 UTC, Joseph Rushton 
Wakeling wrote:
> On 12/12/13 17:19, Adam D. Ruppe wrote:
>> Is that guaranteed to work as an input range? I ask because 
>> I've so often written:
>>
>>   T current;
>>   @property T front() { return current; }
>>
>> that it just seems silly to me to write the extra lines when 
>> current == front. I
>> realize there is a small difference there, in that front is 
>> not an lvalue here,
>> but is when it is a direct member, but other than that, is 
>> this an acceptable
>> form? Or does the lvalue thing mean it is strongly discouraged?
>
> Isn't the issue here not whether or not it will work in terms 
> of your type being a range, and more that it means that users 
> can overwrite the value of front?
>
> It seems to me that it would be OK for personal projects where 
> you control 100% of the code, but it wouldn't be acceptable for 
> stuff that's intended to be used by other people.

Being able to assign to front is a feature of an output range.