Re: x3 semantic action and attribute transformation

> I try in x3 to parse integers which can have seperators '_'. But it
> fails to compile:
>
>           detail::move_to(std::move(src), dest
>           ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
>             , typename attribute_category<Dest>::type());
>             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> etc.
>
> The idea behind is to parse it first into vector<int> and use these rule
> with a semantic action (SA) with a 2nd rule to combine it finally to an
> int. Append the SA directly to the 1st rule also fails to compile.
>
> What is the correct way? Are there any simplifications also? The first
> question seems to me fundamental to be solved.
>
> BTW, why the syntax :
>     auto const integer_def = integer %=
> is there a better one?
>
> Thanks,
> Olaf
>
> ---8<---
> #include <iosfwd>
> //#define BOOST_SPIRIT_X3_DEBUG
>
> #include <boost/spirit/home/x3.hpp>
>
> #include <iostream>
> #include <vector>
> #include <algorithm> // for copy
> #include <iterator>  // for ostream_iterator
> #include <sstream>
>
> namespace parser {
>
>    namespace x3 = boost::spirit::x3;
>    namespace iso8859_1 = boost::spirit::x3::iso8859_1;
>
>    using iso8859_1::char_;
>
>    typedef x3::rule<struct integer_class, uint> integer_type;
>    typedef x3::rule<struct inner_integer_class, std::vector<int>>
> inner_integer_type;
>
>    integer_type const integer { "integer" };
>    inner_integer_type const inner_integer { "inner integer" };
>
>
>    auto combine_to_uint = [](auto &ctx) {
>      auto const &v = x3::_val(ctx);
>      std::ostringstream ss;
>      std::copy(v.begin(), v.end(), std::ostream_iterator<int>(ss, ""));
>      uint int_ { 0 };
>      x3::_pass(ctx) = x3::parse(ss.str().begin(), ss.str().end(),
> x3::uint_, int_);
>      std::cout << int_ << '\n';
>      x3::_attr(ctx) = int_;
>    };
>
>    x3::uint_parser<int, 10, 1, 1>  const digit = { };
>
>    // Parse '1_000' as 1000
>    auto const inner_integer_def =
>      digit >> *( x3::omit[ -char_('_') ] >> digit )
>      ;
>
>    auto const integer_def = integer %= inner_integer[combine_to_uint];
>
>    BOOST_SPIRIT_DEFINE(inner_integer, integer)
> }
>
>
> int main()
> {
>    namespace x3 = boost::spirit::x3;
>
>    std::vector<std::string> const test_cases {
>        "0",
>        "1",
>        "01",
>        "1_000",
>        "42_666_4711",
>        "4_294_967_295", // uint32::max
>        "4_294_967_296" // ??? how to get message about UINT_MAX failed??
>        };
>
>    typedef std::string::const_iterator iterator_type;
>
>    for(auto str: test_cases) {
>      iterator_type iter = str.begin();
>      iterator_type const end = str.end();
>
>      auto& rule = parser::integer;
>
>      std::cout << "parse `" << str << "´:\n";
>
>      std::vector<int> i;
>
>      bool r = x3::phrase_parse(iter, end, rule, x3::space, i);
>
>      if (r && iter == end) {
>        std::cout << "succeeded\n";
>      } else {
>        std::cout << "failed\n";
>      }
>    }
>
>    return 0;
> }
> --->8---

Probably I miss the hook to inform spirit x3 how to move src -> dest. 
Simply x3::_val(ctx) = std::move(int_) doesn't solve it:

x3/support/traits/move_to.hpp:
...detail::move_to_plain ...  [with Source = std::vector<int>; Dest = 
unsigned int, ...
...detail::move_to...[with Source = std::vector<int>; Dest = unsigned 
int, ...


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