Talk:cpp/container/vector

--BohdanKornienko (talk) 13:23, 16 October 2013 (PDT)

Small example to use vector header:

#include <iostream>
#include <vector>

int main(int argc, char **argv)
{
    std::vector<int> vec;

    vec.insert(vec.begin(), 1);
    vec.insert(vec.end(), 2);
    vec.insert(vec.end(), 3);

    vec.erase(vec.begin() + 1);

    std::cout << "count: " << vec.size()
        << "\ncapacity: " << vec.capacity() << std::endl;

    return 0;
}

Pointer/iterator invalidation and vector::assign.

Does vector::assign invalidate iterators? It's not on the list, but I have to assume that if the new size blows the capacity, they have to be invalidated, right? What does the standard say about this?

Neither the simplified summary here nor the actual page (std::vector::assign) say anything about invalidation because the standard (Table 107 — Sequence container requirements) does not say anything about invalidation; it just says "Replaces elements ... with copies of". For input iterators, LLVM libc++ just calls clear and then a series of push_backs, obviously invalidating everything. GNU libstdc++ is a little more careful --Cubbi (talk) 12:09, 22 April 2016 (PDT)

If there's no wording anywhere, I think we'll need an LWG issue, because otherwise the blanket wording in [container.requirements.general]/12 kicks in, which would be obviously wrong. T. Canens (talk) 14:41, 22 April 2016 (PDT)

Ah, it was implied by the old specification pre-LWG2209, but that issue's resolution removed it. T. Canens (talk) 15:41, 24 April 2016 (PDT)

Wrong description of operator[]

It currently describe operator[] as "access or insert specified element", which is incorrect, since std::vector::operator[] never inserts an element, unlike std::map::operator[]. This is because the description uses the standard operator_at template. I'd argue it's better to give a correct description. 2620:0:105F:2:6169:A7F:B58D:284B 01:23, 29 January 2018 (PST)

fixed --D41D8CD98F (talk) 01:29, 29 January 2018 (PST)

The infamous vector<bool>

It's mentioned in the man page but not on any of the member pages. Also, It would be nice if there was more on the main page explaining the limitations - In particular: data() does not exist and &v[0] is not a pointer to bool.

Just noticed that it has its own page but should still probably be referenced from some of the member pages

194.74.130.171 02:06, 19 April 2021 (PDT)

In addition, std::vector<bool>::resize has only one overload:

constexpr void resize(size_type sz, bool c = false);

whilst std::vector<T>::resize() has two overloads:

constexpr void resize(size_type sz);
constexpr void resize(size_type sz, const T& c);

Thus, we need to

--Space Mission (talk) 05:43, 19 April 2021 (PDT)

why is this so difficult?

ive been debugging my code for like an hour but i couldnt create a vector. im so tired rn. XOXO (btw im hot). Jessica (talk) 18:50, 17 September 2023 (PDT)