简单的Spirit X3单词拆分器无法编译，属性不匹配
简单的Spirit X3单词拆分器无法编译，属性不匹配
提问于 2018-08-29 21:46:12
我正在尝试使用Spirit X3解析器来处理来自命令行工具的输出，但是遇到了问题。我已经将它们缩小到一个我不理解其行为的最小示例：
#include <string>
#include <vector>
#include <boost/spirit/home/x3.hpp>
int main() {
namespace x3 = boost::spirit::x3;
std::wstring const str = L"bonjour je suis un petit panda";
auto word = x3::lexeme[+x3::alpha];
std::wstring s;
x3::phrase_parse(begin(str), end(str), word, x3::space, s); // OK
std::vector<std::wstring> v;
x3::phrase_parse(begin(str), end(str), *word, x3::space, v); // Compiler error
}这个错误非常复杂，但归根结底是无法调用move_to，这是属性类型不匹配的症状。
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:180:9: error: no matching function for call to 'move_to'
detail::move_to(std::move(src), dest
^~~~~~~~~~~~~~~
[...]
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:56:9: note: candidate function not viable: no known conversion from 'typename attribute_category<basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t> > >::type' (aka 'boost::spirit::x3::traits::container_attribute') to 'boost::spirit::x3::traits::unused_attribute' for 3rd argument
move_to(Source&&, Dest&, unused_attribute) {}
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:74:9: note: candidate function not viable: no known conversion from 'typename attribute_category<basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t> > >::type' (aka 'boost::spirit::x3::traits::container_attribute') to 'boost::spirit::x3::traits::plain_attribute' for 3rd argument
move_to(Source&& src, Dest& dest, plain_attribute)
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:97:9: note: candidate function not viable: no known conversion from 'typename attribute_category<basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t> > >::type' (aka 'boost::spirit::x3::traits::container_attribute') to 'boost::spirit::x3::traits::tuple_attribute' for 3rd argument
move_to(Source&& src, Dest& dest, tuple_attribute)
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:106:9: note: candidate function not viable: no known conversion from 'typename attribute_category<basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t> > >::type' (aka 'boost::spirit::x3::traits::container_attribute') to 'boost::spirit::x3::traits::tuple_attribute' for 3rd argument
move_to(Source&& src, Dest& dest, tuple_attribute)
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:150:9: note: candidate function not viable: no known conversion from 'typename attribute_category<basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t> > >::type' (aka 'boost::spirit::x3::traits::container_attribute') to 'boost::spirit::x3::traits::variant_attribute' for 3rd argument
move_to(Source&& src, Dest& dest, variant_attribute tag)
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:85:35: note: candidate template ignored: disabled by 'enable_if' [with Source = const wchar_t, Dest = std::__1::basic_string<wchar_t, std::__1::char_traits<wchar_t>, std::__1::allocator<wchar_t> >]
inline typename enable_if<is_container<Source>>::type
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:113:9: note: candidate function template not viable: requires 4 arguments, but 3 were provided
move_to(Source&& src, Dest& dest, variant_attribute, mpl::false_)
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:143:9: note: candidate function template not viable: requires 4 arguments, but 3 were provided
move_to(Source&& src, Dest& dest, variant_attribute, mpl::true_)
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:157:9: note: candidate function template not viable: requires 4 arguments, but 3 were provided
move_to(Iterator, Iterator, unused_type, unused_attribute) {}
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:161:9: note: candidate function template not viable: requires 4 arguments, but 3 were provided
move_to(Iterator first, Iterator last, Dest& dest, container_attribute)
^
/usr/local/include/boost/spirit/home/x3/support/traits/move_to.hpp:171:9: note: candidate function template not viable: requires 4 arguments, but 3 were provided
move_to(Iterator first, Iterator last, boost::iterator_range<Iterator>& rng, container_attribute)
^我的目标是用空格将句子分词。word解析器如预期的那样将第一个完整的单词返回到std::string中。为什么*word不能直接与std::vector<std::string>兼容，我应该写什么呢？
回答 1
Stack Overflow用户
回答已采纳
发布于 2018-08-30 03:38:06
即使对于第一种情况，我也不确定它是否真的有效。
您正在使用ASCII版本的字符解析器(x3::alpha是x3::standard::alpha的同义词)，传递的迭代器值类型为wchar_t，但对于非ascii字符，boost::spirit::char_encoding::standard::ischar()将返回false。
对于x3::standard_wide::alpha，它是有效的：
#include <string>
#include <vector>
#include <boost/spirit/home/x3.hpp>
int main() {
namespace x3 = boost::spirit::x3;
std::wstring const str = L"bonjour je suis un petit panda";
auto word = x3::lexeme[+x3::standard_wide::alpha];
std::wstring s;
x3::phrase_parse(begin(str), end(str), word, x3::space, s); // OK
std::vector<std::wstring> v;
x3::phrase_parse(begin(str), end(str), *word, x3::space, v); // OK
}另一个很好的问题是它是否适用于ASCII，以及x3::standard::space和x3::standard_wide::space之间是否存在差异(由于Unicode，人们可能会将更多的字符视为空格)。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/52078975
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