ideas about ranges

[Lionello Lunesu]

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...

L.