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Boost spirit: What types of names should be used for embedded terminals?

I am refactoring the input system (model type) that I use, uses the spirit for string serialization. I use the type-time compile-time simulation construct.

template<> type_traits<int4_type> { typedef boost::spirit::qi::int_parser<boost::int32_t> string_parser; } template<> type_traits<string_type> { typedef boost::spirit::ascii::string string_parser; }

In this example, I show primitive parsers, but I expect to introduce rules as well.

The int4 type works, but this is because of (home / qi / numeric / int.hpp +27):

 namespace tag { template <typename T, unsigned Radix, unsigned MinDigits , int MaxDigits> struct int_parser {}; } namespace qi { /////////////////////////////////////////////////////////////////////// // This one is the class that the user can instantiate directly in // order to create a customized int parser template <typename T = int, unsigned Radix = 10, unsigned MinDigits = 1 , int MaxDigits = -1> struct int_parser : spirit::terminal<tag::int_parser<T, Radix, MinDigits, MaxDigits> > {}; }

typedef string does not work and does not eps. I could not understand why referring to the line parser. However, in the case of eps, it boils down to:

 #define BOOST_SPIRIT_TERMINAL(name) \ namespace tag { struct name {}; } \ typedef boost::proto::terminal<tag::name>::type name##_type; \ name##_type const name = {{}}; \ inline void silence_unused_warnings__##name() { (void) name; } \ /***/

This means that I cannot typedef it, it is a proto-terminal constructor or an opaque global definition of const.

My question is: how do I type a rule, grammar, primitive parser?

Note. I have already begun work on providing all of my “types” with a functor that encapsulates a rule and then creates a type trait.

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I'm not sure if this will work in all cases, but what I did for typedef, my skipper should have used BOOST_TYPEOF:

 typedef BOOST_TYPEOF(boost::spirit::ascii::space - (boost::spirit::qi::eol | boost::spirit::qi::eoi)) SkipperT;

so your example will be

 typedef BOOST_TYPEOF(boost::spirit::ascii::string) string_parser;

There is probably a better / more elegant way, but currently it works for what I need.

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