Scope Containers

[Atila Neves]

On Sunday, 10 March 2019 at 17:36:09 UTC, bitwise wrote:
> On Sunday, 10 March 2019 at 16:10:10 UTC, Atila Neves wrote:
>> On Sunday, 10 March 2019 at 15:12:03 UTC, bitwise wrote:
>>> [...]
>>
>> Like `const`, `scope` on a member function means that the 
>> `this` reference is `scope`.
>
> Interesting. I'll have to look up some examples.
>
>>> [...]
>>
>> https://github.com/atilaneves/automem/blob/2a97acba94d6fe0bf9ba07fec99e86e46aa0f2a1/source/automem/vector.d#L134
>> https://github.com/atilaneves/automem/blob/2a97acba94d6fe0bf9ba07fec99e86e46aa0f2a1/source/automem/vector.d#L159
>> https://github.com/atilaneves/automem/blob/2a97acba94d6fe0bf9ba07fec99e86e46aa0f2a1/source/automem/vector.d#L145
>>
>> static assert(isInputRange!(Vector!int));
>>
>>> [...]
>>
>> I would think so, especially since I wrote Vector to be @safe 
>> with dip1000. Look at this unit test for not being able to 
>> escape the payload for example:
>>
>> https://github.com/atilaneves/automem/blob/master/tests/ut/vector.d#L229
>
> Ok, but this container copies the entire collection in postblit:
> https://github.com/atilaneves/automem/blob/2a97acba94d6fe0bf9ba07fec99e86e46aa0f2a1/source/automem/vector.d#L104

Well, yes. As it says in the module ddoc, it's my version of 
C++'s std::vector. If you don't want it to copy, pass by ref.

> So if you try to treat it like a range, you'll take a 
> performance hit every time you trigger the postblit, which 
> seems likely.

You can pass it by ref like I mention above, or you could slice 
it and pass the slice instead. Without DIP1000 passing the slice 
wouldn't be @safe but with it, it is.

Again, just like std::vector, which is pretty much always passed 
by const ref. But safer and with a default allocator.

> Isn't it reasonable to assume a range should act like a 
> reference to data, rather than a copy of it?

It depends.