annulen at yandex.ru
Wed Apr 26 23:38:56 CEST 2017
26.04.2017, 08:04, "Marc Mutz" <marc.mutz at kdab.com>:
> On 2017-04-25 23:04, Thiago Macieira wrote:
>> On Tuesday, 25 April 2017 17:49:16 -03 Alejandro Exojo wrote:
>>> On Tuesday 25 April 2017 16:35:01 Thiago Macieira wrote:
>>> > QVector and QList don't have the same API. They're slightly different.
>>> > What'sm ore, QList has a beginning-of-list optimisation, whereas QVector
>>> > doesn't (not even my copy, I stopped development shortly before I got to
>>> > that part, even if I did add a QArrayData::GrowsBackward flag to support
>>> > the case).
>>> > (...)
>>> > So, no, we can't implement that in Qt 5. In Qt 6, we've already agreed we
>>> > don't want this mess, so QList as it is simply goes away.
>>> By the way, which is the exit strategy for QQueue?
>> Do we need one?
>> The only reason that QQueue uses QList is because QList has that
>> optimisation, while QVector does not. Once we implement that for
>> QVector, we
>> should be able to use QQueue with QVector too.
> FWIW: I'm against adding even more pessimising goodies to QVector. An
> area for push_front is such a goodie. The addition this causes is
> probably the reason why a QList, even for optimal payloads, is
> outperformed by QVector in my well-known benchmark from -Wmarc. Users
> that need a queue can use std::deque. If you don't iterate over it, it's
> a more than acceptable container.
std::deque is not a contiguous container, unlike QList or QVector, so it cannot be a
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