Trying to implement a bi directional range and it is slightly unclear what the semantics are supposed to be and just wanted some clarification.

Are bidirectional ranges supposed to be able to support switching direction mid iteration? Like if I do popFront popFront popBack should that be equal to just a single popFront? Or once you start on a direction should switching be considered an error? Or is popFront and popBack supposed to consume from both ends of the range and the range is empty when they meet?

-tofu

On Wednesday, 23 September 2015 at 02:10:22 UTC, Tofu Ninja wrote:
> Trying to implement a bi directional range and it is slightly unclear what the semantics are supposed to be and just wanted some clarification.
>
> Are bidirectional ranges supposed to be able to support switching direction mid iteration? Like if I do popFront popFront popBack should that be equal to just a single popFront? Or once you start on a direction should switching be considered an error? Or is popFront and popBack supposed to consume from both ends of the range and the range is empty when they meet?
>
> -tofu

The last one. E.g. for arrays (except narrow strings... ugh)

auto popFront(T)(ref T[] a)
{
    a = a[1 .. $];
}

auto popBack(T)(ref T[] a)
{
    a = a[0 .. $-1];
}

On Wednesday, 23 September 2015 at 03:26:29 UTC, John Colvin wrote:
> On Wednesday, 23 September 2015 at 02:10:22 UTC, Tofu Ninja wrote:
>> Trying to implement a bi directional range and it is slightly unclear what the semantics are supposed to be and just wanted some clarification.
>>
>> Are bidirectional ranges supposed to be able to support switching direction mid iteration? Like if I do popFront popFront popBack should that be equal to just a single popFront? Or once you start on a direction should switching be considered an error? Or is popFront and popBack supposed to consume from both ends of the range and the range is empty when they meet?
>>
>> -tofu
>
> The last one. E.g. for arrays (except narrow strings... ugh)
>
> auto popFront(T)(ref T[] a)
> {
>     a = a[1 .. $];
> }
>
> auto popBack(T)(ref T[] a)
> {
>     a = a[0 .. $-1];
> }

Ok cool, that's what I ended up doing.