如何使用 boost::date_time 解析一年中的几周？

发布于 2024-12-13 06:37:17 字数 641 浏览 0 评论 0原文

我想解析由 4 位数年份和一年中的周数组成的字符串。我遵循了 boost date/time IO 教程，生成了一个如下的测试示例：

std::string week_format = "%Y-W%W";
boost::date_time::date_input_facet<boost::gregorian::date, char> week_facet =     boost::date_time::date_input_facet<boost::gregorian::date, char>(week_format);

std::stringstream input_ss;
input_ss.imbue(locale(input_ss.getloc(), &week_facet));

std::string input_week = "2004-W34";
input_ss.str(input_week);

boost::gregorian::date input_date;
input_ss >> input_date;

不幸的是，input_date 只是打印为“2004-01-01”，这意味着它刚刚解析了年份。我做错了什么？ %W 在输入时不可用吗？（文档没有这样标记。）

原文

I want to parse strings that consist of a 4-digit year and the week number within the year. I've followed the boost date/time IO tutorial, producing a test example like this:

std::string week_format = "%Y-W%W";
boost::date_time::date_input_facet<boost::gregorian::date, char> week_facet =     boost::date_time::date_input_facet<boost::gregorian::date, char>(week_format);

std::stringstream input_ss;
input_ss.imbue(locale(input_ss.getloc(), &week_facet));

std::string input_week = "2004-W34";
input_ss.str(input_week);

boost::gregorian::date input_date;
input_ss >> input_date;

Unfortunately, input_date just prints as "2004-01-01", implying that it just parsed the year. What am I doing wrong? Is %W not available on input? (The documentation doesn't mark it as such.)

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小糖芽 2024-12-20 06:37:17

您是正确的，文档没有在“格式标志”部分中将其标记为这样（旁边没有“！”...）

http://www.boost.org/doc/libs/1_35_0/doc/html/date_time/date_time_io.html#date_time.format_flags

但这似乎是一个疏忽。因为在 Boost 的 format_date_parser.hpp 中，parse_date 中没有覆盖这种情况...您可以查看 switch 语句并看到：

http://svn.boost.org/svn/boost/trunk/boost/date_time/format_date_parser.hpp

尽管没有任何代码可以做到这一点，但即使是源代码中的注释也说它在解析输入时处理 %W 和 %U。这是怎么回事？ :-/

另一方面，我相信 week_facet 需要在您的示例中动态分配：（

std::string week_format = "%Y-W%W";
boost::date_time::date_input_facet<boost::gregorian::date, char>* week_facet =
    new boost::date_time::date_input_facet<boost::gregorian::date, char>(
        week_format
    );

std::stringstream input_ss;
input_ss.imbue(std::locale(input_ss.getloc(), week_facet));

或者至少我必须这样做以防止示例崩溃。）

You are correct that the documentation doesn't mark it as such in the "Format Flags" section (no "!" next to it...)

http://www.boost.org/doc/libs/1_35_0/doc/html/date_time/date_time_io.html#date_time.format_flags

But that seems to be an oversight. Because in Boost's format_date_parser.hpp there is no coverage for this case in parse_date...you can look at the switch statement and see that:

http://svn.boost.org/svn/boost/trunk/boost/date_time/format_date_parser.hpp

Despite the absence of any code to do it, even the comments in the source say it handles %W and %U on parse input. What's up with that? :-/

On another note, I believe week_facet needs to be dynamically allocated in your example:

std::string week_format = "%Y-W%W";
boost::date_time::date_input_facet<boost::gregorian::date, char>* week_facet =
    new boost::date_time::date_input_facet<boost::gregorian::date, char>(
        week_format
    );

std::stringstream input_ss;
input_ss.imbue(std::locale(input_ss.getloc(), week_facet));

(Or at least I had to do it that way to keep the example from crashing.)

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