ideas about ranges

[Andrei Alexandrescu]

Lionello Lunesu wrote:
> Andrei Alexandrescu wrote:
>> Steven Schveighoffer wrote:
>>> Another idea is to make the T the ref'd arg, similar to how the 
>>> system call read() works:
>>>
>>> bool popNext(ref T);
>>>
>>> This has some benefits:
>>>
>>> 1) you aren't checking a temporary for emptyness, so it fits well 
>>> within a loop construct
>>> 2) you can avoid returning a dummy element in the empty range case.
>>> 3) you avoid returning a piece of possibly large data on the stack 
>>> when it's probably just going to get copied anyways (although the 
>>> compiler can sometimes optimize this).
>>
>> We considered that as well. It is problematic because looking at 
>> elements always entails copying them, which is rather silly if you do 
>> it for e.g. an array.
>>
>> By golly, I kid you not but the interface I personally like the most is:
>>
>> struct ArchetypalInputRange(T)
>> {
>>     T* popNext();
>> }
>>
>> popNext returns a pointer to a T (the value may be reused) or null 
>> when the range is done. Iteration becomes easy and efficient for all 
>> types. An input range would still have to keep a buffer (and return a 
>> pointer to it), but things are not awkward to implement.
>>
>> Given the bad reputation that pointers have, I guess people wouldn't 
>> like this all that much.
> 
> You don't need a pointer to T, you need a nullable T :)
> ...which doesn't exist...

You need a nullable reference to T...

Andrei