Here follows a simple pattern to use Boost.Spirit to create a
"parseable" object, with a bonus formatted input operator, allowing you
quick access to formatter input for your type.
(Yeah, this stuff needs tweaking for better error handling, etc.)
class foo_thing {
public:
/* Other methods and stuff. */
template <typename ForwardIterator>
boost::spirit::parse_info<IteratorT>
parse (ForwardIterator begin, ForwardIterator end);
private:
class grammar;
/* Data members, etc. */
};
template
std::basic_istream&
operator>> (std::basic_istream& i, foo_thing& thing) {
using namespace std;
using namespace boost::spirit;
typedef multi_pass iterator_t;
iterator_t begin(i);
iterator_t end = make_multi_pass(istreambuf_iterator<CharT>());
/* What if thing.parse() throws? */
parse_info info = thing.parse(begin, end);
if (!info.hit)
i.setstate(ios_base::failbit);
return i;
}
class foo_thing::grammar : public
boost::spirit::grammar {
public:
grammar (foo_thing& thing) : _M_thing(thing) {}
template <typename ScannerT>
class definition;
private:
foo_thing mutable& _M_thing;
};
template <typename ScannerT>
class foo_thing::grammar::definition {
public:
/* Define this one; your parser ultimately writes to self._M_thing. */
definition (foo_thing::grammar const& self);
boost::spirit::rule<ScannerT> const& start () const;
private:
/* Populate with rules. */
};
template <typename IteratorT>
boost::spirit::parse_info<IteratorT>
foo_thing::parse (IteratorT begin, IteratorT end) {
namespace s = boost::spirit;
grammar g(*this);
s::parse_info<IteratorT> r = s::parse(begin, end, g);
return r;
}
--
Pedro Lamarão
Desenvolvimento
Intersix Technologies S.A.
SP: (55 11 3803-9300)
RJ: (55 21 3852-3240)
www.intersix.com.br
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