range behaviour

[Steven Schveighoffer via Digitalmars-d]

On Tue, 13 May 2014 12:58:09 -0400, Jonathan M Davis via Digitalmars-d  
<digitalmars-d at puremagic.com> wrote:

> On Tue, 13 May 2014 18:38:44 +0200
> Benjamin Thaut via Digitalmars-d <digitalmars-d at puremagic.com> wrote:
>
>> I know that there was a recent discussion about how the methods of
>> ranges should behave.
>>
>> E.g.
>>
>> - Does empty always have to be called before calling front or
>> popFront?
>
> Certainly, ranges are pretty much always used this way, but there was  
> some
> debate as to whether empty could have work done in it (and thus _had_ to  
> be
> called). However, I believe that the consensus was that yes, empty had  
> to be
> called (certainly, both Walter and Andrei felt that way).

I don't agree there was a consensus. I think empty should not have to be  
called if it's already logically known that the range is not empty. The  
current documentation states that, and I don't think there was an  
agreement that we should change it, despite the arguments from Walter.

In any case, I think generic code for an unknown range type in an unknown  
condition should have to call empty, since it cannot logically prove that  
it's not.

Even if it was required, it would be an unenforceable policy, just like  
range.save.

-Steve