thanks for our answer ! Your solution work, but it is not exactly I want. Indeed this expression return the typename of a tag (for example literal-char) instead its value ( "A" , "B" , .... ). for example if my start rule is start = qi::char_("a-z") > qi::char_("!"); and I parse the string "a#" then I expect that _4 contain "!" , phx::bind(&boost::spirit::info::tag, qi::_4) return "literal-char" 2 questions : a) I have a look in boost::spirit::info class is the boost::spirit::info::value member is containing the data I want ( ie "!") b) perhaps it exists an alternative like phx::construct<>( phx::val("") << _4 ) thanks again Vincent Agnus Le 06/04/2011 17:07, TONGARI a écrit :

2011/4/6 TONGARI mailto:tongari95@gmail.com>

2011/4/6 Vincent Agnus mailto:vincent.agnus@ircad.fr>

How can a get qi::_4 as string ?

phx::bind(&boost::spirit::info::tag, qi::_4)

Well, this may or may not be what you want, though...

qi::_4 here stands for a boost::spirit::info object which seems not documented yet. Anyway, it's not a string, but it's outputable (traverse through its value, a tree structure), so its tag member (a utf8_string) is not identical to what will be output, you can see your BOOST_ROOT/boost/spirit/home/support/info.hpp

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

Le 06/04/2011 20:08, TONGARI a écrit :

Does my first suggestion solve your first attempt? i.e. (ostream&)m_error << ...

I don't have see our answer in our previous mail. I have test it with m_error as std::stringstream and phx::ref( (ostream&)m_error ). And it works fine !!! Thanks a lot for our help Note that there is a compilation error with *std::ostringstream* m_error and phx::ref( m_error )

for example if my start rule is start = qi::char_("a-z") > qi::char_("!");

and I parse the string "a#" then I expect that _4 contain "!" , phx::bind(&boost::spirit::info::tag, qi::_4) return "literal-char"

2 questions : a) I have a look in boost::spirit::info class is the boost::spirit::info::value member is containing the data I want ( ie "!")

True here, but it's a more subtle thing than I can explain... Not every case can you get a utf8_string form boost::spirit::info::value.

For example, "... > qi::char_('a', 'z')" you can get the value as a utf8_string "a-z"; while "... > qi::char_("a-z")" you can only get a nil object from value.

OK

b) perhaps it exists an alternative like phx::construct<>( phx::val("") << _4 )

I don't know what you mean here.

With this kind of proposition I will hope to hack the string construction (m_error in this case is a std::string). a) phx::constructstd::string( phx::val("...") ) is a valid expression b) phx::val("...") << _4 is a valid expression c) phx::constructstd::string( phx::val("...") << _4 ). The evaluation on this expression first compute (exp. b) phx::val("...") << _4 then then apply (a) evaluation. For my application I will use our workarond, thanks again Vincent Agnus