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Empty std::array<T, 0> doesn't have constexpr begin()?

By : amandeep singh
Date : July 30 2020, 04:00 PM
This might help you I believe this is a bug in libc++ which was introduced in: https://reviews.llvm.org/D41223
In particular, the _LIBCPP_CONSTEXPR_AFTER_CXX14 is missing on begin(), end(), etc.
code :

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constexpr array of constexpr objects using move ctor

By : user2840954
Date : March 29 2020, 07:55 AM
I hope this helps you . I have a class with a constexpr value constructor, but no copy or move ctor ,
So who is right here?

non-member function begin()/cbegin() and its constexpr-ness

By : mightysweaty
Date : March 29 2020, 07:55 AM
seems to work fine Current constexpr support in the Standard Library is indeed rather limited.
non-member std::begin is not marked constexpr because apart from array and initializer-list, no Standard Container (or container like entity such as bitset) supports constexpr member begin() (mainly because some implementations want to use iterator debugging using dynamic memory allocation). Your interpretation here is correct. non-member std::cbegin is marked constexpr in order to support the (currently) two constexpr std::begin non-member functions for array and initializer_list, and to be forward-compatible for future upgrades in the Standard Library.

My code doesnt work when passed in .begin() as parameter but works after i convert .begin() into an iterator

By : mehmet sandık
Date : March 29 2020, 07:55 AM
may help you . The definition void erase(iterator&i, iterator&j) is rather suspect.
iterator& means that you have to have an existing variable to bind to the (non-const) reference. Iterators are by design "pointer-equivalents", which would normally be passed by value. You wouldn't write void erase(string*&i, string*&j).

mgo golang doesnt update empty array using $set

By : user1749098
Date : March 29 2020, 07:55 AM
it fixes the issue struct and method: , MediaFilterExceptionUserIds type should change from []int to *[]int,
code :
type Group struct {
    Id                          int64             `bson:"_id,omitempty"`
    MediaFilterExceptionUserIds *[]int            `bson:"media_filter_exception_user_ids,omitempty"`
group.MediaFilterExceptionUserIds = &[]int{}

constexpr begin of a std::array

By : ynakashima
Date : March 29 2020, 07:55 AM
wish help you to fix your issue I am having trouble understanding why both gcc-8.2.0 and clang-7.0.0 reject the following code (live code here): , So let's sidestep std::array to make this a bit easier:
code :
template <typename T, size_t N>
struct array {
    T elems[N];

    constexpr T const* begin() const { return elems; }

void foo() {
    constexpr array<int,3> v{{1, 2, 3}};
    constexpr auto b = v.begin(); // error

constexpr array<int, 3> global_v{{1, 2, 3}};
constexpr auto global_b = global_v.begin(); // ok
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