yohhoy

// https://groups.google.com/g/golang-nuts/c/Gze1TRtdLdc/m/RoD2AxssDgAJ
// http://svr-pes20-cppmem.cl.cam.ac.uk/cppmem/
int main() {
  int x = 0; 
  atomic_int int y = 0;
  {{{ { x = 1;
        y.store(1);
        x = 1;
        y.store(1); }
  ||| { y.load().readsvalue(0);

yohhoy

Full barrier

P: =p0=\ /----\ /=p1=\ /----\ /=
        *      *      *      *
C: ----/ \=c0=/ \----/ \=c1=/ \-

Half barrier

P: p0=\--------/=p1=\--------/=

yohhoy

#include <ctime>
#include <chrono>
#include <iostream>
#include <iomanip>

namespace std {

// https://timsong-cpp.github.io/cppwp/n4868/time.cal.ymd.nonmembers#14
// "yyyy-mm-dd"
inline ostream& operator<<(ostream& os, const chrono::year_month_day& ymd) {

yohhoy

// requires C++23 or later
#include <bit>
#include <concepts>

template <std::integral T>
constexpr T hton(T value) noexcept
{
  if constexpr (std::endian::native == std::endian::little) {
    return std::byteswap(value);
  } else {

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/*
 * Convert from OpenCV image and write movie with FFmpeg
 *
 * Copyright (c) 2021 yohhoy
 */
#include <iostream>
#include <vector>
// FFmpeg
extern "C" {
#include <libavformat/avformat.h>

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#include <algorithm>
#include <iostream>
#include <string>
#include <string_view>
#include <ranges>

int main() {
  std::string_view str = "apple,banana,cinnamon";
  for (auto rev_item: str | std::views::reverse | std::views::split(',')) {
     static_assert( std::ranges::forward_range<decltype(rev_item)>);

yohhoy

prog.cc: In function 'int main()':
prog.cc:6:19: error: no match for 'operator|' (operand types are 'std::forward_list<int, std::allocator<int> >' and 'const std::ranges::views::_Reverse')
    6 |   for (int _: lst | std::views::reverse) {}
      |               ~~~ ^ ~~~~~~~~~~~~~~~~~~~
      |               |                 |
      |               |                 const std::ranges::views::_Reverse
      |               std::forward_list<int, std::allocator<int> >
In file included from prog.cc:2:
/opt/wandbox/gcc-head/include/c++/12.0.0/ranges:818:7: note: candidate: 'template<class _Lhs, class _Rhs>  requires (derived_from<_Lhs, std::ranges::views::__adaptor::_RangeAdaptorClosure>) && (derived_from<_Rhs, std::ranges::views::__adaptor::_RangeAdaptorClosure>) constexpr auto std::ranges::views::__adaptor::operator|(_Lhs, _Rhs)'
  818 |       operator|(_Lhs __lhs, _Rhs __rhs)

yohhoy

#include <initializer_list>

namespace mock {
  template <class T>
  struct allocator {};
  template <class T>
  struct char_traits {};

  // C++20 https://timsong-cpp.github.io/cppwp/n4861/basic.string
  template<class charT, class traits = char_traits<charT>,

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bool starts_with_utf8bom(std::string_view s)
{
  constexpr char utf8_bom[3] = { 0xEF, 0xBB, 0xBF };
  return s.length() >= 3 && std::equal(utf8_bom, utf8_bom + 3, s.begin());
}

std::string& erase_utf8bom(std::string& text)
{
  if (starts_with_utf8bom(text)) {
    text.erase(0, 3);

yohhoy

#include <type_traits>

int main() {
  int x = 42;
  static_assert(std::is_same_v<decltype( x ), int>);
  static_assert(std::is_same_v<decltype((x)), int&>);

  int (y) = 42;  // redundant parentheses
  static_assert(std::is_same_v<decltype( y ), int>);
  static_assert(std::is_same_v<decltype((y)), int&>);