Reece Dunn wrote:
I have been learning Boost.Spirit over the past few days and here are a few queries:
[1] Is it possible to process a token stream rather than a character stream? If so, are there any examples? The reason I am asking is...
Yes. See Hartmut Kaiser's Wave CPP preprocessor.
[2] Is it possible to cascade spirit grammars, e.g.
wave.parse() >> cpp.parse(); // hypothetical
Yes.
where the output of the wave grammar feeds the token stream of the cpp grammar. I am not propsing that the above is how this would be expressed.
[3] Is it possible to combine the file_iterator with the position_iterator to provide error reporting on that?
Yes.
[4] I am now making use of boost::spirit::sub_grammar from libs/spirit/doc/techniques.html. One thing I get from this is that the typedef for the grammar type can be very difficult to read, especially for non-trivial grammars! I have started writing a set of type helpers to simplify the process:
namespace boost { namespace spirit { template< typename T1, typename T2, typename T3 > struct alternative3_t { typedef alternative< alternative< T1, T2 >, T3 > type; };
template< typename T1, typename T2, typename T3 > struct sequence3_t { typedef sequence< sequence< T1, T2 >, T3 > type; };
// confix_type = T1 >> *( CompositeT - T2 ) >> T2
template< typename CompositeT, typename T1 = strlit< const char *
, typename T2 = T1 > struct confix_t { typedef typename sequence3_t < T1, kleene_star< difference< CompositeT, T2 > >, T2 >::type type; };
template< typename T2 = strlit< const char * >, typename T1 = strlit< const char * > > struct comment_t { typedef typename confix_t< anychar_parser, T1, T2 >::type type; };
typedef comment_t< chlit< char > >::type line_comment; typedef comment_t<>::type range_comment; }}
using these, the typedef for the skip_grammar example becomes:
typedef typename boost::spirit::alternative3_t < boost::spirit::space_parser, boost::spirit::line_comment, boost::spirit::range_comment
::type start_t;
If there is interest, I shall create a proper submission for them.
Oh, very cool! That would be very nifty indeed. Cheers, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net