如何解析条目后面跟分号或换行符（boost :: spirit）？

本文介绍了如何解析条目后面跟分号或换行符（boost :: spirit）？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 在Boost :: Spirit中，如何解析后面跟有分号或带有可选分号的换行符的条目？ In Boost::Spirit, how can I parse entries that are followed by either a semicolon or by a newline with optional semicolon? 输入示例，其中每个条目都是int和double：Example input, where each entry is an int and a double:12 1.4;63 13.22423 56.4 ; 5 8.1这里是只解析空格的条目的示例代码：Here is example code that just parses entries followed by whitespace:#include <iostream>#include <boost/foreach.hpp>#include <boost/spirit/include/qi.hpp>#include <boost/spirit/include/support_istream_iterator.hpp>#include <boost/fusion/include/std_pair.hpp>namespace qi = boost::spirit::qi;typedef std::pair<int, double> Entry;template <typename Iterator, typename Skipper>struct MyGrammar : qi::grammar<Iterator, std::vector<Entry>(), Skipper> { MyGrammar() : MyGrammar::base_type(entries) { entry = qi::int_ >> qi::double_; entries = +entry; } qi::rule<Iterator, Entry(), Skipper> entry; qi::rule<Iterator, std::vector<Entry>(), Skipper> entries;};int main() { typedef boost::spirit::istream_iterator It; std::cin.unsetf(std::ios::skipws); It it(std::cin), end; MyGrammar<It, qi::space_type> entry_grammar; std::vector<Entry> entries; if (qi::phrase_parse(it, end, entry_grammar, qi::space, entries) && it == end) { BOOST_FOREACH(Entry const& entry, entries) { std::cout << entry.first << " and " << entry.second << std::endl; } } else { std::cerr << "FAIL" << std::endl; exit(1); } return 0;}现在，解析我想要的方式（每个条目后跟分号或换行符用可选的分号），我替换了：Now, to parse the way I want (each entry followed by semicolon or newline with optional semicolon), I replaced this: entries = +entry;： entries = +(entry >> (qi::no_skip[qi::eol] || ';'));其中 boost :: spirit code> || 表示：（a后跟可选b）或b。但如果在此示例输入中 1.4 后面有空格，则会出错：where the boost::spirit operator || means: (a followed by optional b) or b. But gives an error if there is a space after the 1.4 in this example input:12 1.463 13.2因为 no_skip 但我找不到解决方案。It makes sense that the space is not matched because of the no_skip but I wasn't able to find a solution.推荐答案这是我的采访。 您可能想要了解 qi :: blank c $ c> qi :: space except qi :: eol ）。这将删除 no_skip 的需要。 核心语法变为：You might want to know about qi::blank (which is qi::space except qi::eol). This will remove the need for no_skip. The core grammar becomes: entry = qi::int_ >> qi::double_; entries = entry % +qi::char_("\n;") >> qi::omit[*qi::space]; 使用BOOST_SPIRIT_DEBUG了解解析失败的原因和原因（例如回溯） 输出：12 and 1.463 and 13.22423 and 56.45 and 8.1完整代码：//#define BOOST_SPIRIT_DEBUG#include <iostream>#include <boost/foreach.hpp>#include <boost/spirit/include/qi.hpp>#include <boost/spirit/include/support_istream_iterator.hpp>#include <boost/fusion/include/std_pair.hpp>namespace qi = boost::spirit::qi;typedef std::pair<int, double> Entry;template <typename Iterator, typename Skipper>struct MyGrammar : qi::grammar<Iterator, std::vector<Entry>(), Skipper> { MyGrammar() : MyGrammar::base_type(entries) { entry = qi::int_ >> qi::double_; entries = entry % +qi::char_("\n;") // the data >> qi::omit[*qi::space] > qi::eoi; // trailing whitespace BOOST_SPIRIT_DEBUG_NODE(entry); BOOST_SPIRIT_DEBUG_NODE(entries); } qi::rule<Iterator, Entry(), Skipper> entry; qi::rule<Iterator, std::vector<Entry>(), Skipper> entries;};int main() { typedef boost::spirit::istream_iterator It; std::cin.unsetf(std::ios::skipws); It it(std::cin), end; MyGrammar<It, qi::blank_type> entry_grammar; std::vector<Entry> entries; if (qi::phrase_parse(it, end, entry_grammar, qi::blank, entries) && it == end) { BOOST_FOREACH(Entry const& entry, entries) { std::cout << entry.first << " and " << entry.second << std::endl; } } else { std::cerr << "FAIL" << std::endl; exit(1); } return 0;} 这篇关于如何解析条目后面跟分号或换行符（boost :: spirit）？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！