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我在使用 karma 为保存在 boost::shared_ptrs 向量中的结构生成输出时遇到了一些麻烦。我有一个使用无法编译的整数的小测试用例。我在想我可以使用 deref_iterator 自定义点来处理这种情况，或者开箱即用的精神可能会注意到我的容器持有指针类型并执行额外的取消引用。无论如何，这是测试用例：

#include <boost/spirit/include/karma.hpp>
#include <boost/shared_ptr.hpp>
#include <vector>

typedef boost::shared_ptr< int > ptr;
typedef std::vector< ptr > vec;

namespace boost {
namespace spirit {
namespace traits {

// specialise how iterators into containers of pointers are dereferenced
template <>
struct deref_iterator< typename container_iterator< vec const >::type >
{
    typedef int type;

    static
    type
    call( typename container_iterator< vec const >::type & it ) {
        return **it;
    }
};

} // namespace traits
} // namespace spirit
} // namespace boost



int
main() {
    vec v;
    v.push_back( ptr( new int( 1 ) ) );
    v.push_back( ptr( new int( 2 ) ) );
    v.push_back( ptr( new int( 3 ) ) );

    using namespace boost::spirit::karma;
    using boost::spirit::ascii::space;

    generate_delimited(
        std::ostream_iterator< char >( std::cout ),
        *int_,
        space,
        v
    );

    return 0;
}

这是编译错误：

...patience...
...patience...
...found 1986 targets...
...updating 3 targets...
gcc.compile.c++ /home/john/Dev/Bio/bin/Bio/gcc-4.6/release/src/spirit/vector-of-ptrs.o
In file included from /home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/numeric/bool_policies.hpp:16:0,
from /home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/numeric/bool.hpp:29,
from /home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/numeric.hpp:13,
from /home/john/src/boost/boost_1_51_0/boost/spirit/home/karma.hpp:15,
from /home/john/src/boost/boost_1_51_0/boost/spirit/include/karma.hpp:16,
from src/spirit/vector-of-ptrs.cpp:1:
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/numeric/detail/numeric_utils.hpp: In static member function ‘static boost::shared_ptr<
        int> boost::spirit::traits::absolute_value<boost::shared_ptr<int>, void>::call(boost::shared_ptr<int>)’:
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/numeric/detail/numeric_utils.hpp:149:41:   instantiated from ‘boost::spirit::traits::absolute_value<boost::shared_ptr<int> >::ame boost
    ::spirit::traits::absolute_value<T>::type = boost::shared_ptr<int> boost::spirit::traits::get_absolute_value(boost::shared_ptr<int>)’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/numeric/int.hpp:213:57:   instantiated from ‘static bool boost::spirit::karma::any_int_generator<
        int, boost::spirit::unused_type, boost::spirit::unused_type, 10u, false
    >::insert_int(boost::spirit::karma::detail::output_iterator<ostream_iterator<char>, mpl_::int_<0>, boost::spirit::unused_type> &, const boost::shared_ptr<int> &)’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/numeric/int.hpp:242:39:   instantiated from ‘static bool boost::spirit::karma::any_int_generator<
        int, boost::spirit::unused_type, boost::spirit::unused_type, 10u, false
    >::generate(
        boost::spirit::karma::detail::output_iterator<ostream_iterator<char>, mpl_::int_<0>, boost::spirit::unused_type> &, boost::spirit::context<
            boost::fusion::cons<const vector<boost::shared_ptr<int> > &, boost::fusion::nil>, boost::spirit::locals<> > &, const boost::spirit::karma::any_space<boost::spirit::char_encoding::ascii> &
      , const boost::shared_ptr<int> &)’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/detail/fail_function.hpp:36:62:   instantiated from ‘bool boost::spirit::karma::detail::fail_function<
        boost::spirit::karma::detail::output_iterator<ostream_iterator<char>, mpl_::int_<0>, boost::spirit::unused_type>, boost::spirit::context<
            boost::fusion::cons<const vector<boost::shared_ptr<int> > &, boost::fusion::nil>, boost::spirit::locals<> >, boost::spirit::karma::any_space<boost::spirit::char_encoding::ascii> >
    ::operator()(const boost::spirit::karma::any_int_generator<int, boost::spirit::unused_type, boost::spirit::unused_type, 10u, false> &, const boost::shared_ptr<int> &) const’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/detail/pass_container.hpp:274:13:   instantiated from ‘bool boost::spirit::karma::detail::pass_container<
        boost::spirit::karma::detail::fail_function<
            boost::spirit::karma::detail::output_iterator<ostream_iterator<char>, mpl_::int_<0>, boost::spirit::unused_type>, boost::spirit::context<
                boost::fusion::cons<const vector<boost::shared_ptr<int> > &, boost::fusion::nil>, boost::spirit::locals<> >, boost::spirit::karma::any_space<boost::spirit::char_encoding::ascii> >,
        vector<boost::shared_ptr<int> >, boost::spirit::karma::detail::indirect_iterator<vector<boost::shared_ptr<int> >::const_iterator>, mpl_::bool_<false> 
    >::dispatch_container(const boost::spirit::karma::any_int_generator<int, boost::spirit::unused_type, boost::spirit::unused_type, 10u, false> &, mpl_::mpl_::bool_<false>) const’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/detail/pass_container.hpp:321:61:   [ skipping 2 instantiation contexts ]
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/operator/kleene.hpp:53:32:   instantiated from ‘bool boost::spirit::karma::base_kleene<
        boost::spirit::karma::any_int_generator<int, boost::spirit::unused_type, boost::spirit::unused_type, 10u, false>, mpl_::bool_<false>, boost::spirit::karma::kleene<
            boost::spirit::karma::any_int_generator<int, boost::spirit::unused_type, boost::spirit::unused_type, 10u, false> > 
    >::generate_subject(
        boost::spirit::karma::detail::pass_container<
            boost::spirit::karma::detail::fail_function<
                boost::spirit::karma::detail::output_iterator<ostream_iterator<char>, mpl_::int_<0>, boost::spirit::unused_type>, boost::spirit::context<
                    boost::fusion::cons<const vector<boost::shared_ptr<int> > &, boost::fusion::nil>, boost::spirit::locals<> >, boost::spirit::karma::any_space<boost::spirit::char_encoding::ascii> >
          , vector<boost::shared_ptr<int> >, boost::spirit::karma::detail::indirect_iterator<vector<boost::shared_ptr<int> >::const_iterator>, mpl_::bool_<false> >, const vector<
            boost::shared_ptr<int> > &, mpl_::mpl_::bool_<false>) const’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/operator/kleene.hpp:126:17:   instantiated from ‘bool boost::spirit::karma::base_kleene<
        boost::spirit::karma::any_int_generator<int, boost::spirit::unused_type, boost::spirit::unused_type, 10u, false>, mpl_::bool_<false>, boost::spirit::karma::kleene<
            boost::spirit::karma::any_int_generator<int, boost::spirit::unused_type, boost::spirit::unused_type, 10u, false> > 
    >::generate(
        boost::spirit::karma::detail::output_iterator<ostream_iterator<char>, mpl_::int_<0>, boost::spirit::unused_type> &, boost::spirit::context<
            boost::fusion::cons<const vector<boost::shared_ptr<int> > &, boost::fusion::nil>, boost::spirit::locals<> > &, const boost::spirit::karma::any_space<boost::spirit::char_encoding::ascii> &
      , const vector<boost::shared_ptr<int> > &) const’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/generate.hpp:161:53:   instantiated from ‘bool boost::spirit::karma::generate_delimited(
        boost::spirit::karma::detail::output_iterator<ostream_iterator<char>, mpl_::int_<0> > &, const boost::proto::exprns_::expr<
            boost::proto::tagns_::tag::dereference, boost::proto::argsns_::list1<const boost::spirit::terminal<boost::spirit::tag::int_> &>, 1l> &, const boost::proto::exprns_::expr<
            boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0l> &, boost::spirit
        ::karma::delimit_flag::enum_type, const vector<boost::shared_ptr<int> > &)’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/generate.hpp:185:82:   instantiated from ‘bool boost::spirit::karma::generate_delimited(
        ostream_iterator<char> &, const boost::proto::exprns_::expr<boost::proto::tagns_::tag::dereference, boost::proto::argsns_::list1<const boost::spirit::terminal<boost::spirit::tag::int_> &>,
            1l> &, const boost::proto::exprns_::expr<
            boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0l> &, boost::spirit
        ::karma::delimit_flag::enum_type, const vector<boost::shared_ptr<int> > &)’
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/generate.hpp:227:48:   instantiated from ‘bool boost::spirit::karma::generate_delimited(
        const ostream_iterator<char> &, const boost::proto::exprns_::expr<
            boost::proto::tagns_::tag::dereference, boost::proto::argsns_::list1<const boost::spirit::terminal<boost::spirit::tag::int_> &>, 1l> &, const boost::proto::exprns_::expr<
            boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0l> &, const vector<
            boost::shared_ptr<int> > &)’
src/spirit/vector-of-ptrs.cpp:46:2:   instantiated from here
/home/john/src/boost/boost_1_51_0/boost/spirit/home/karma/numeric/detail/numeric_utils.hpp:60:26: error: No match for ‘fabs(boost::shared_ptr<int> &)’

STL Decryptor reminder:
    Use the /cand:L option to see all suppressed template candidates

    "/home/john/src/stlfilt/gfilt"  -ftemplate-depth-128 -Wno-deprecated -Wno-unused -Wno-error -O3 -finline-functions -Wno-inline -Wall -fPIC -Wno-deprecated -Wno-unused -DBOOST_FILESYSTEM_VERSION=3 -DNDEBUG -DWITH_NONAMESPACES -DXML_LIBRARY  -I"../Bio" -I"../Hmm" -I"/home/john/src/boost/boost_1_51_0" -c -o "/home/john/Dev/Bio/bin/Bio/gcc-4.6/release/src/spirit/vector-of-ptrs.o" "src/spirit/vector-of-ptrs.cpp"

...failed gcc.compile.c++ /home/john/Dev/Bio/bin/Bio/gcc-4.6/release/src/spirit/vector-of-ptrs.o...
...removing /home/john/Dev/Bio/bin/Bio/gcc-4.6/release/src/spirit/vector-of-ptrs.o
...skipped <p/home/john/Dev/Bio/bin/Bio/gcc-4.6/release>spirit-vector-of-ptrs for lack of <p/home/john/Dev/Bio/bin/Bio/gcc-4.6/release>src/spirit/vector-of-ptrs.o...
...failed updating 1 target...
...skipped 1 target...
4

1 回答 1

6

一些实验使我找到了未按预期实例化特化的原因：迭代器在生成器表达式的求karma::detail::indirect_iterator值过程中已被包裹（with） 。

这是对我有用的修复：

namespace boost {
namespace spirit {
namespace traits {

    // specialise how iterators into containers of pointers are dereferenced
    template <>
        struct deref_iterator< karma::detail::indirect_iterator<vec::const_iterator> >
    {
        typedef karma::detail::indirect_iterator<vec::const_iterator> It;
        typedef int type;

        static type call( It const & it ) {
            return **it;
        }
    };

} // namespace traits
} // namespace spirit
} // namespace boost
于 2012-09-06T23:52:59.113 回答