C++ 如何使用qi::hold[]解析器指令。(boost::swap的属性类型存在问题)
我有一个解析器,可以解析成C++ 如何使用qi::hold[]解析器指令。(boost::swap的属性类型存在问题),c++,boost,swap,boost-spirit,boost-spirit-qi,C++,Boost,Swap,Boost Spirit,Boost Spirit Qi,我有一个解析器,可以解析成boost::variant 这在第一行“Sarai”中失败。如果我像这样反转double和int的解析: value = qi::double_ | qi::int_ | qi::lexeme[+(qi::char_ - qi::eol)] ; value = qi::hold[qi::int_] | qi::hold[qi::double_] | qi::lexeme[+(qi::char_ - qi::eol)] ; 它工作正常,但是“Janelle”的
boost::variant
这在第一行“Sarai”中失败。如果我像这样反转double和int的解析:
value = qi::double_ | qi::int_ | qi::lexeme[+(qi::char_ - qi::eol)] ;
value = qi::hold[qi::int_] | qi::hold[qi::double_] | qi::lexeme[+(qi::char_ - qi::eol)] ;
它工作正常,但是“Janelle”的整数值被解析为double。在和之后,我想像这样使用qi::hold[]:
value = qi::double_ | qi::int_ | qi::lexeme[+(qi::char_ - qi::eol)] ;
value = qi::hold[qi::int_] | qi::hold[qi::double_] | qi::lexeme[+(qi::char_ - qi::eol)] ;
但有了这个,我得到了一个关于缺少函数的消息:swap()
。这实际上记录在boost文档中(注意)。但解释非常简洁。我找不到此交换函数的正确属性类型。有人能帮忙吗
此处的编译器消息:
E:\Boost\boost_1_58_0\boost/spirit/home/support/attributes.hpp(1036) : error C2784: 'void boost::spirit::swap(boost::spirit::multi_pass<T,Policies> &,boost::spirit::multi_pass<T,Policies> &)' : could not deduce template argument for 'boost::spirit::multi_pass<T,Policies> &' from 'int'
我对“Rebekah”的值有疑问。我还看到,评估值的顺序很重要。这一次,问题不再是double
值,而是int
和字符串之间的问题。我想实施这样的东西:(政策?)
只有数字、可选减号和包含点的所有内容都是double
只有数字和可选减号的所有内容都是int
其他一切都是std::string
解决方案
有时候,理解问题比理解问题更重要
问题不是解析器策略,而是我对解析规则的定义(见上文)。规则3“其他所有内容”实际上包括:“截至EOL的所有内容”。因此,值
规则中的所有三个备选方案必须与此匹配:
value = strict_double >> qi::eol
| qi::int_ >> qi::eol
| qi::lexeme[+(qi::char_ - qi::eol)] >> qi::eol;
有了这个变化,就像一个魅力 保持不用于此操作
想想看:这会有什么帮助?它不会使整数分支不匹配,因此它仍然无法解析,并且hold
不会还原任何内容
hold[]
主要用于容器属性,其中部分解析可能会修改属性。容器通常已经实现了交换。你找错人了
包括字符串,参见例如
解决问题:
您可以使用严格实数策略仅将实数值解析为double
value = strict_double | qi::int_ | qi::lexeme[+(qi::char_ - qi::eol)] ;
// with
qi::real_parser<double, qi::strict_real_policies<double> > strict_double;
和调试信息(如果启用)
莎拉:52.731
莎拉:52.731
莎拉:52.731
莎拉:52.731
: 52.731199473801
[S,a,r,a,i]]
52.731199473801\n
\nJamiya:果冻
[52.7312]
杰米娅:果冻
[S,a,r,a,i],52.7312]
杰米娅:果冻
杰米娅:果冻
:果冻滴
[J,a,m,i,y,a]]
果冻滴\n果冻
\nClara:-92.4
[J,e,l,l,y,D,r,o,p]]
克拉拉:-92.40
[J,a,m,i,y,a],[J,e,l,l,y,D,r,o,p]]
克拉拉:-92.40
克拉拉:-92.40
: -92.40860586988
[C,l,a,r,a]]
-92.408605869885
\nJanelle:13234
[-92.4086]
珍妮尔:132349
[C,l,a,r,a],-92.4086]]
珍妮尔:132349
珍妮尔:132349
:132349223\n文件
[J,a,n,e,l,l,e]]
132349223\n布里利
\恩布里利:-40.9
[132349223]
布里利:-40.90
[J,a,n,e,l,l,e],132349223]
布里利:-40.90
布里利:-40.90
: -40.90535249560
[B,r,i,l,e,y]]
-40.905352495602
\n
[-40.9054]
[B,r,i,l,e,y],-40.9054]
[B,r,i,l,e,y],-40.9054],[C,l,a,r,a],-92.4086],[J,a,m,i,y,a],[J,e,l,l,y,D,r,o,p],[J,a,n,e,l,l,e],132349223],[S,a,r,a,i],52.7312]]
[B,r,i,l,e,y],-40.9054],[C,l,a,r,a],-92.4086],[J,a,m,i,y,a],[J,e,l,l,y,D,r,o,p],[J,a,n,e,l,l,e],132349223],[S,a,r,a,i],52.7312]]
非常感谢!我还有很多东西要学;-)但是请看一下我对这个问题的更新。是否有类似于严格的\u整型\u策略
?
value = strict_double | qi::int_ | qi::lexeme[+(qi::char_ - qi::eol)] ;
// with
qi::real_parser<double, qi::strict_real_policies<double> > strict_double;
#define BOOST_SPIRIT_DEBUG
#include <boost/fusion/adapted/std_pair.hpp>
#include <boost/spirit/include/qi.hpp>
#include <map>
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
typedef boost::variant<int, double, std::string> value_t;
typedef std::map<std::string, value_t> namevalue;
typedef std::pair<std::string, value_t> namevaluepair;
template <typename Iterator>
struct keys_and_values2
: qi::grammar<Iterator, namevalue(), ascii::blank_type>
{
keys_and_values2() : keys_and_values2::base_type(start)
{
start %= query >> qi::eoi;
query = +pair;
value = strict_double | qi::int_ | qi::lexeme[+(qi::char_ - qi::eol)] ;
pair = key >> qi::lit(':') >> value >> qi::eol;
key = qi::char_("a-zA-Z_") >> *qi::char_("a-zA-Z_0-9");
BOOST_SPIRIT_DEBUG_NODES((start)(query)(value)(pair)(key))
}
private:
qi::real_parser<double, qi::strict_real_policies<double> > strict_double;
qi::rule<Iterator, namevalue(), ascii::blank_type> start;
qi::rule<Iterator, namevalue(), ascii::blank_type> query;
qi::rule<Iterator, namevaluepair(), ascii::blank_type> pair;
qi::rule<Iterator, std::string(), ascii::blank_type> key;
qi::rule<Iterator, value_t(), ascii::blank_type> value;
};
int main() {
typedef boost::spirit::istream_iterator It;
It f(std::cin >> std::noskipws), l;
keys_and_values2<It> g;
namevalue data;
bool ok = qi::phrase_parse(f,l,g,ascii::blank,data);
if (ok) {
std::cout << "Parse succeeded:\n";
for(auto& p : data)
std::cout << "\t'" << p.first << "'\t-> " << p.second << "\n";
} else
std::cout << "Parse failed\n";
if (f!=l)
std::cout << "Remaining unparsed: '" << std::string(f,l) << "'\n";
}
Parse succeeded:
'Briley' -> -40.9054
'Clara' -> -92.4086
'Jamiya' -> Jelly Drop
'Janelle' -> 132349223
'Sarai' -> 52.7312
<start>
<try>Sarai : 52.731</try>
<query>
<try>Sarai : 52.731</try>
<pair>
<try>Sarai : 52.731</try>
<key>
<try>Sarai : 52.731</try>
<success>: 52.731199473801</success>
<attributes>[[S, a, r, a, i]]</attributes>
</key>
<value>
<try> 52.731199473801\n</try>
<success>\nJamiya : Jelly</success>
<attributes>[52.7312]</attributes>
</value>
<success>Jamiya : Jelly </success>
<attributes>[[[S, a, r, a, i], 52.7312]]</attributes>
</pair>
<pair>
<try>Jamiya : Jelly </try>
<key>
<try>Jamiya : Jelly </try>
<success>: Jelly Drop\nClar</success>
<attributes>[[J, a, m, i, y, a]]</attributes>
</key>
<value>
<try> Jelly Drop\nClara</try>
<success>\nClara : -92.4</success>
<attributes>[[J, e, l, l, y, , D, r, o, p]]</attributes>
</value>
<success>Clara : -92.40</success>
<attributes>[[[J, a, m, i, y, a], [J, e, l, l, y, , D, r, o, p]]]</attributes>
</pair>
<pair>
<try>Clara : -92.40</try>
<key>
<try>Clara : -92.40</try>
<success>: -92.40860586988</success>
<attributes>[[C, l, a, r, a]]</attributes>
</key>
<value>
<try> -92.408605869885</try>
<success>\nJanelle : 13234</success>
<attributes>[-92.4086]</attributes>
</value>
<success>Janelle : 132349</success>
<attributes>[[[C, l, a, r, a], -92.4086]]</attributes>
</pair>
<pair>
<try>Janelle : 132349</try>
<key>
<try>Janelle : 132349</try>
<success>: 132349223\nBrile</success>
<attributes>[[J, a, n, e, l, l, e]]</attributes>
</key>
<value>
<try> 132349223\nBriley</try>
<success>\nBriley : -40.9</success>
<attributes>[132349223]</attributes>
</value>
<success>Briley : -40.90</success>
<attributes>[[[J, a, n, e, l, l, e], 132349223]]</attributes>
</pair>
<pair>
<try>Briley : -40.90</try>
<key>
<try>Briley : -40.90</try>
<success>: -40.90535249560</success>
<attributes>[[B, r, i, l, e, y]]</attributes>
</key>
<value>
<try> -40.905352495602</try>
<success>\n</success>
<attributes>[-40.9054]</attributes>
</value>
<success></success>
<attributes>[[[B, r, i, l, e, y], -40.9054]]</attributes>
</pair>
<pair>
<try></try>
<key>
<try></try>
<fail/>
</key>
<fail/>
</pair>
<success></success>
<attributes>[[[[B, r, i, l, e, y], -40.9054], [[C, l, a, r, a], -92.4086], [[J, a, m, i, y, a], [J, e, l, l, y, , D, r, o, p]], [[J, a, n, e, l, l, e], 132349223], [[S, a, r, a, i], 52.7312]]]</attributes>
</query>
<success></success>
<attributes>[[[[B, r, i, l, e, y], -40.9054], [[C, l, a, r, a], -92.4086], [[J, a, m, i, y, a], [J, e, l, l, y, , D, r, o, p]], [[J, a, n, e, l, l, e], 132349223], [[S, a, r, a, i], 52.7312]]]</attributes>
</start>