C++ 以字符串格式 YYYYMMDD 减去天数

Question

我正在努力获取一些 C++ 代码进行协作。有没有一种直接的方法可以减去两个字符串日期？我正在尝试获取它们之间的天数。它们是字符串，YYYYMMDD。 Boost 库是正确的方向吗？

Answer 1

是的，Boost Date_Time当然可以做到这一点，甚至其他人也可能会建议“更轻”的替代方案。

这里是关于 days alive 的例子，它几乎完全解决了你的问题(只需添加第二个日期解析):

/* Short example that calculates the number of days since user was born.
 * Demonstrates comparisons of durations, use of the day_clock,
 * and parsing a date from a string.
 */

#include "boost/date_time/gregorian/gregorian.hpp"
#include <iostream>

int
main() 
{

  using namespace boost::gregorian;
  std::string s;
  std::cout << "Enter birth day YYYY-MM-DD (eg: 2002-02-01): ";
  std::cin >> s;
  try {
    date birthday(from_simple_string(s));
    date today = day_clock::local_day();
    days days_alive = today - birthday;
    days one_day(1);
    if (days_alive == one_day) {
      std::cout << "Born yesterday, very funny" << std::endl;
    }
    else if (days_alive < days(0)) {
      std::cout << "Not born yet, hmm: " << days_alive.days() 
                << " days" <<std::endl;
    }
    else {
      std::cout << "Days alive: " << days_alive.days() << std::endl;
    }

  }
  catch(...) {
    std::cout << "Bad date entered: " << s << std::endl;
  }
  return 0;
}