is std.algorithm.joiner lazy?

[Puming via Digitalmars-d-learn]

On Friday, 8 April 2016 at 08:44:36 UTC, Mike Parker wrote:
> On Friday, 8 April 2016 at 03:20:53 UTC, Puming wrote:
>> On Friday, 8 April 2016 at 02:49:01 UTC, Jonathan M Davis 
>> wrote:
>>> [...]
>>
>> Thanks. I'll adopt this idiom. Hopefully it gets used often 
>> enough to warrent a phobos function :-)
>
> What would such a function look like? I don't think such a 
> thing could exist. This is more than just an idiom, IMO. It's a 
> basic principle of ranges that, if not followed, is likely to 
> produce a broken range and/or one whose front is more expensive 
> than it needs to be. The trouble is that it isn't necessarily 
> obvious and is easy to overlook when first implementing a 
> custom range.
>

I thought it was just like map!readNext.cache


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