Function read_input

example/cpp20/operations/c_callback_wrapper.cpp:21–32

// plus void* context idiom for exposing a callback.

void read_input(const char* prompt, void (*cb)(void*, const char*), void* arg)
{
  std::thread(
      [prompt = std::string(prompt), cb, arg]
      {
        std::cout << prompt << ": ";
        std::cout.flush();
        std::string line;
        std::getline(std::cin, line);
        cb(arg, line.c_str());
      }).detach();
}

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