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

[Joseph Rushton Wakeling]

On Saturday, 14 December 2013 at 15:26:36 UTC, Jakob Ovrum wrote:
> On Friday, 13 December 2013 at 14:52:32 UTC, Marco Leise wrote:
>> Most non-trivial ranges do the actual work in `popFront()' and
>> return a cached value from `front'. It has been argued as a
>> design quirk, that this in general leads to:
>
> Really? I've never seen that particular pattern. I always just 
> see the initial element being computed when the range is 
> initialized, e.g. in a constructor or a constructor helper 
> function.

I don't know about "most non-trivial ranges" but it is a pattern 
that shows up when you have a struct that cannot be guaranteed to 
be properly initialized upon creation -- which is a common 
situation because structs don't allow a default constructor 
this().