yohhoy

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

yohhoy

#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>,

yohhoy

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&>);

yohhoy

#include <memory>
#include <vector>
#define SPDLOG_ACTIVE_LEVEL SPDLOG_LEVEL_DEBUG
#include "spdlog/spdlog.h"
#include "spdlog/sinks/stdout_color_sinks.h"
#include "spdlog/sinks/daily_file_sink.h"
#include "spdlog/sinks/rotating_file_sink.h"

int main(int argc, char* argv[])
{

yohhoy

//
// requires Micosoft VisualC++ 2019 16.3 Preview 2 that implements P0717R1.
//
// https://devblogs.microsoft.com/cppblog/c20-concepts-are-here-in-visual-studio-2019-version-16-3/
// https://wg21.link/p0717r1 Semantic constraint matching for concepts
#include <type_traits>

#if 1
template <class T, class U>
concept same_as_impl = std::is_same_v<T, U>;

yohhoy

constraint-expressions:
- C1<T>^c && C2<T>^c
- C1<T>^d

# concept version
template <class T> concept C1<T> = true^a;
template <class T> concept C2<T> = true^b;

normal form of P = true^a ∧ true^b
normal form of Q = true^a

yohhoy

/*
 * https://github.com/intel/ffmpeg_libyami/blob/master/libavutil/timecode.c
 */
inline int av_timecode_init_from_string2(AVTimecode* tc, AVRational rate, const char* str)
{
#if 0
	return av_timecode_init_from_string(&tc, rate, str, NULL);
#else
	char c;
	int hh, mm, ss, ff;