Hi Andre,
.resize(0) actually deletes the storage. Farrakh is wanting it to
preserve the storage (keep the .capacity(), not have to alloc it again)

Farrakh,
I think that you might not realize the reason .clear() is slower is
because it has to call the in-place destructor for each element (zero
through size(), but not all the way up to .capacity()) You can't just
change the count or you screw up the object lifetime of those objects
that were not destructed. D'tors won't get called. Index positions may
potentially get overwritten later with subsequent push_backs(...) and the
in-place c'tors calls. (thus causing leaks)

https://en.cppreference.com/w/cpp/container/vector/clear


On Fri, Dec 27, 2024 at 2:08 PM Andre Kostur via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> What’s wrong with .resize(0) ?
>
> On Fri, Dec 27, 2024 at 1:57 PM Фаррах Фаттахов via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
>> After working with SFML, I so hated std::vector (I was a bad programmer
>> back then and didn't know about the reserve() function, which led to not
>> understanding why std::vector is so slow, while a simple array performs
>> much better). As a result, in my new project i created my own version of
>> std::vector - FE2D::dynamic_array. And there, from the beginning i created
>> one useful function - reset()
>> ```C++
>>
>> // Reset the Size of Dynamic Array to Zero, but it's don't Touches the Real Occupied Memory of Dynamic Array
>> void reset() { mSize = 0; }
>> ```
>>
>> Instead of clear() it's just setting mSize to zero. It's very useful in
>> the situations like
>>
>> ```C++
>> void Render() { // It's called every frame
>> // Add a sprites to the FE2D::dynamic_array to draw it later
>> m_Renderer.AddSprite(m_Sprite_0);
>> m_Renderer.AddSprite(m_Sprite_1);
>> m_Renderer.AddSprite(m_Sprite_2);
>> ...
>> // Draw the Sprites and reset the dynamic arrays to prepare it for the next frame
>> m_Renderer.RenderSprites();
>> }
>> ```
>> Here reset() works like clear(), but much faster
>>
>> In the std::vector or std::deque is no functions like reset() and i want
>> to add it there, especially sometimes i get errors because my
>> FE2D::dynamic_array is not so good like std::vector and i have to use it
>> instead of mine, but there is no function i need. I think reset() will be
>> nice thing for std::vector.
>> --
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>>
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