问题
edit : I have ripped out the lexer as it does not cleanly integrate with Qi and just obfuscates grammars (see here).
on_success isn't well documented and I am trying to wire it up to my parser. The examples dealing with on_success deal with parsers just built on qi --i.e., no lex.
This is how I am trying to introduce the construct :
using namespace qi::labels;
qi::on_success(event_entry_,std::cout << _val << _1);
But it won't compile. I am dreading the problem being lex. Could someone tell me what I am doing wrong and secondly tell me what all placeholders are available, there type and what they represent (since they aren't documented).
The full file is as follows:
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/home/phoenix/bind/bind_member_variable.hpp>
#include <boost/spirit/include/lex_lexertl.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/none.hpp>
#include <boost/cstdint.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <string>
#include <exception>
#include <vector>
namespace lex = boost::spirit::lex;
namespace px = boost::phoenix;
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
template <typename Lexer>
struct tokens : lex::lexer<Lexer>
{
tokens()
: left_curly("\"{\""),
right_curly("\"}\""),
left_paren("\"(\""),
right_paren("\")\""),
colon(":"),
scolon(";"),
namespace_("(?i:namespace)"),
event("(?i:event)"),
optional("(?i:optional)"),
required("(?i:required)"),
repeated("(?i:repeated)"),
t_int_4("(?i:int4)"),
t_int_8("(?i:int8)"),
t_string("(?i:string)"),
ordinal("\\d+"),
identifier("\\w+")
{
using boost::spirit::lex::_val;
this->self
=
left_curly [ std::cout << px::val("lpar") << std::endl]
| right_curly [ std::cout << px::val("rpar") << std::endl]
| left_paren
| right_paren
| colon [ std::cout << px::val("colon") << std::endl]
| scolon
| namespace_ [ std::cout << px::val("kw namesapce") << std::endl]
| event [ std::cout << px::val("kw event") << std::endl]
| optional [ std::cout << px::val("optional ") << "-->" << _val << "<--" << std::endl]
| required [ std::cout << px::val("required") << std::endl]
| repeated
| t_int_4
| t_int_8
| t_string
| ordinal [ std::cout << px::val("val ordinal (") << _val << ")" << std::endl]
| identifier [std::cout << px::val("val identifier(") << _val << ")" << std::endl];
this->self("WS") = lex::token_def<>("[ \\t\\n]+");
}
lex::token_def<lex::omit> left_curly, right_curly, colon, scolon,repeated, left_paren, right_paren;
lex::token_def<lex::omit> namespace_, event, optional, required,t_int_4, t_int_8, t_string;
lex::token_def<boost::uint32_t> ordinal;
lex::token_def<> identifier;
};
enum event_entry_qualifier
{
ENTRY_OPTIONAL,
ENTRY_REQUIRED,
ENTRY_REPEATED
};
enum entry_type
{
RBL_INT4,
RBL_INT8,
RBL_STRING,
RBL_EVENT
};
struct oid
{
boost::uint32_t ordinal;
std::string name;
};
BOOST_FUSION_ADAPT_STRUCT
(
oid,
(boost::uint32_t, ordinal)
(std::string, name)
)
struct type_descriptor
{
entry_type type_id;
std::string referenced_event;
};
BOOST_FUSION_ADAPT_STRUCT
(
type_descriptor,
(entry_type, type_id)
(std::string, referenced_event)
)
struct event_entry
{
event_entry_qualifier qualifier;
oid identifier;
type_descriptor descriptor;
};
BOOST_FUSION_ADAPT_STRUCT
(
event_entry,
(event_entry_qualifier, qualifier)
(oid, identifier)
(type_descriptor, descriptor)
)
struct event_descriptor
{
oid identifier;
std::vector<event_entry> event_entries;
};
BOOST_FUSION_ADAPT_STRUCT
(
event_descriptor,
(oid, identifier)
(std::vector<event_entry>, event_entries)
)
template <typename Iterator, typename Lexer>
struct grammar : qi::grammar<Iterator,event_descriptor(), qi::in_state_skipper<Lexer> >
{
template <typename TokenDef>
grammar(TokenDef const& tok)
: grammar::base_type(event_descriptor_)
{
using qi::_val;
//start = event;
event_descriptor_ = tok.event >> oid_ >> tok.left_curly >> *(event_entry_) >> tok.right_curly;
event_entry_ = event_qualifier >> oid_ >> type_descriptor_ >> tok.scolon;
event_qualifier = tok.optional [ _val = ENTRY_OPTIONAL]
| tok.required [ _val = ENTRY_REQUIRED]
| tok.repeated [ _val = ENTRY_REPEATED];
oid_ = tok.ordinal
>> tok.colon
>> tok.identifier;
type_descriptor_
= (( atomic_type >> qi::attr(""))
| ( event_type >> tok.left_paren >> tok.identifier >> tok.right_paren));
atomic_type = tok.t_int_4 [ _val = RBL_INT4]
| tok.t_int_8 [ _val = RBL_INT8]
| tok.t_string [ _val = RBL_STRING];
event_type = tok.event [_val = RBL_EVENT];
using namespace qi::labels;
qi::on_success(event_entry_,std::cout << _val << _1);
}
qi::rule<Iterator> start;
qi::rule<Iterator, event_descriptor(), qi::in_state_skipper<Lexer> > event_descriptor_;
qi::rule<Iterator, event_entry(), qi::in_state_skipper<Lexer> > event_entry_;
qi::rule<Iterator, event_entry_qualifier()> event_qualifier;
qi::rule<Iterator, entry_type()> atomic_type;
qi::rule<Iterator, entry_type()> event_type;
qi::rule<Iterator, type_descriptor(),qi::in_state_skipper<Lexer> > type_descriptor_;
qi::rule<Iterator, oid()> oid_;
};
std::string test = " EVENT 1:sihan { OPTIONAL 123:hassan int4; OPTIONAL 123:hassan int4; } ";
int main()
{
typedef lex::lexertl::token<std::string::iterator, boost::mpl::vector<boost::uint32_t, std::string> > token_type;
typedef lex::lexertl::actor_lexer<token_type> lexer_type;
typedef tokens<lexer_type>::iterator_type iterator_type;
tokens<lexer_type> token_lexer;
grammar<iterator_type,tokens<lexer_type>::lexer_def> grammar(token_lexer);
std::string::iterator it = test.begin();
iterator_type first = token_lexer.begin(it, test.end());
iterator_type last = token_lexer.end();
bool r;
r = qi::phrase_parse(first, last, grammar, qi::in_state("WS")[token_lexer.self]);
if(r)
;
else
{
std::cout << "parsing failed" << std::endl;
}
}
回答1:
Looking at the header files I think the meaning of the placeholders is:
_1 = Iterator position when the rule was tried.
_2 = Iterator to the end of the input.
_3 = Iterator position right after the rule has been successfully matched.
(Since I'm not sure that the lines above are understandable, here's a little example with your input)
rule being tried
_________________________________
´ `
[EVENT][1][:][sihan][{][OPTIONAL][123][:][hassan][int4][;][OPTIONAL][321][:][hassan2][int4][;][}]
_1 _3 _2
As GManNickG mentions in the comments these are lexer iterators, and you can't access easily the original string with them. The conjure2 example combines the use of a lexer and on_error/on_success. To accomplish that it uses a special kind of token, position_token. This token always has access to the pair of iterators of the original string associated with itself (the normal token loses this information when you use lex::omit). position_token has several interesting methods. matched() returns an iterator_range<OriginalIterator>, and begin() and end() return the corresponding iterators.
In the code below I chose to create a phoenix::function that takes two lexer iterators (called with _1 and _3) and returns a string that covers the distance between them (using std::string(begin_iter->begin(), end_iter->begin())).
One problem I found was that the fact that the whitespace was in a diferent state caused that the iterators the position_token returned were invalid. What I did to solve this was put everything in the same state and then simply use lex::_pass = lex::pass_flags::pass_ignore with the whitespace.
The last (minor) problem is that if you want to use std::cout << _val you need to define operator<< for the types you are interested in.
PS: I always use BOOST_SPIRIT_USE_PHOENIX_V3 and this requires that every spirit/phoenix include comes from boost/spirit/include/.... If, for any reason, you need/want to use V2 you'll need to change the phoenix::function. I also am incapable of using an old style for loop, so if you can't use c++11 you'll have to change the definition of operator<< for event_descriptor.
#define BOOST_SPIRIT_USE_PHOENIX_V3
// #define BOOST_SPIRIT_DEBUG
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_bind.hpp> //CHANGED
#include <boost/spirit/include/lex_lexertl.hpp>
#include <boost/spirit/include/lex_lexertl_position_token.hpp> //ADDED
#include <boost/none.hpp>
#include <boost/cstdint.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <string>
#include <exception>
#include <vector>
namespace lex = boost::spirit::lex;
namespace px = boost::phoenix;
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
template <typename Lexer>
struct tokens : lex::lexer<Lexer>
{
tokens()
: left_curly("\"{\""),
right_curly("\"}\""),
left_paren("\"(\""),
right_paren("\")\""),
colon(":"),
scolon(";"),
namespace_("(?i:namespace)"),
event("(?i:event)"),
optional("(?i:optional)"),
required("(?i:required)"),
repeated("(?i:repeated)"),
t_int_4("(?i:int4)"),
t_int_8("(?i:int8)"),
t_string("(?i:string)"),
ordinal("\\d+"),
identifier("\\w+")
{
using boost::spirit::lex::_val;
this->self
=
left_curly //[ std::cout << px::val("lpar") << std::endl]
| right_curly //[ std::cout << px::val("rpar") << std::endl]
| left_paren
| right_paren
| colon //[ std::cout << px::val("colon") << std::endl]
| scolon
| namespace_ // [ std::cout << px::val("kw namesapce") << std::endl]
| event // [ std::cout << px::val("kw event") << std::endl]
| optional //[ std::cout << px::val("optional ") << "-->" << _val << "<--" << std::endl]
| required //[ std::cout << px::val("required") << std::endl]
| repeated
| t_int_4
| t_int_8
| t_string
| ordinal //[ std::cout << px::val("val ordinal (") << _val << ")" << std::endl]
| identifier //[std::cout << px::val("val identifier(") << _val << ")" << std::endl]
| lex::token_def<>("[ \\t\\n]+") [lex::_pass = lex::pass_flags::pass_ignore] //CHANGED
;
}
lex::token_def<lex::omit> left_curly, right_curly, left_paren, right_paren, colon, scolon;
lex::token_def<lex::omit> namespace_, event, optional, required, repeated, t_int_4, t_int_8, t_string;
lex::token_def<boost::uint32_t> ordinal;
lex::token_def<> identifier;
};
enum event_entry_qualifier
{
ENTRY_OPTIONAL,
ENTRY_REQUIRED,
ENTRY_REPEATED
};
enum entry_type
{
RBL_INT4,
RBL_INT8,
RBL_STRING,
RBL_EVENT
};
struct oid
{
boost::uint32_t ordinal;
std::string name;
};
BOOST_FUSION_ADAPT_STRUCT
(
oid,
(boost::uint32_t, ordinal)
(std::string, name)
)
std::ostream& operator<<(std::ostream& os, const oid& val) //ADDED
{
return os << val.ordinal << "-" << val.name;
}
struct type_descriptor
{
entry_type type_id;
std::string referenced_event;
};
BOOST_FUSION_ADAPT_STRUCT
(
type_descriptor,
(entry_type, type_id)
(std::string, referenced_event)
)
std::ostream& operator<<(std::ostream& os, const type_descriptor& val) //ADDED
{
return os << val.type_id << "-" << val.referenced_event;
}
struct event_entry
{
event_entry_qualifier qualifier;
oid identifier;
type_descriptor descriptor;
};
BOOST_FUSION_ADAPT_STRUCT
(
event_entry,
(event_entry_qualifier, qualifier)
(oid, identifier)
(type_descriptor, descriptor)
)
std::ostream& operator<<(std::ostream& os, const event_entry& val) //ADDED
{
return os << val.qualifier << "-" << val.identifier << "-" << val.descriptor;
}
struct event_descriptor
{
oid identifier;
std::vector<event_entry> event_entries;
};
BOOST_FUSION_ADAPT_STRUCT
(
event_descriptor,
(oid, identifier)
(std::vector<event_entry>, event_entries)
)
std::ostream& operator<<(std::ostream& os, const event_descriptor& val) //ADDED
{
os << val.identifier << "[";
for(const auto& entry: val.event_entries) //C++11
os << entry;
os << "]";
return os;
}
struct build_string_impl //ADDED
{
template <typename Sig>
struct result;
template <typename This, typename Iter1, typename Iter2>
struct result<This(Iter1,Iter2)>
{
typedef std::string type;
};
template <typename Iter1, typename Iter2>
std::string operator()(Iter1 begin, Iter2 end) const
{
return std::string(begin->begin(),end->begin());
}
};
px::function<build_string_impl> build_string;
template <typename Iterator, typename Lexer>
struct grammar : qi::grammar<Iterator,event_descriptor() >
{
template <typename TokenDef>
grammar(TokenDef const& tok)
: grammar::base_type(event_descriptor_)
{
using qi::_val;
//start = event;
event_descriptor_ = tok.event >> oid_ >> tok.left_curly >> *(event_entry_) >> tok.right_curly;
event_entry_ = event_qualifier >> oid_ >> type_descriptor_ >> tok.scolon;
event_qualifier = tok.optional [ _val = ENTRY_OPTIONAL]
| tok.required [ _val = ENTRY_REQUIRED]
| tok.repeated [ _val = ENTRY_REPEATED];
oid_ = tok.ordinal
>> tok.colon
>> tok.identifier;
type_descriptor_
= (( atomic_type >> qi::attr(""))
| ( event_type >> tok.left_paren >> tok.identifier >> tok.right_paren));
atomic_type = tok.t_int_4 [ _val = RBL_INT4]
| tok.t_int_8 [ _val = RBL_INT8]
| tok.t_string [ _val = RBL_STRING];
event_type = tok.event [_val = RBL_EVENT];
using namespace qi::labels;
qi::on_success(event_entry_,std::cout << _val << " " << build_string(_1,_3) << std::endl); //CHANGED
// BOOST_SPIRIT_DEBUG_NODES( (event_descriptor_)(event_entry_)(event_qualifier)(oid_)(type_descriptor_)(atomic_type)(event_type) );
}
qi::rule<Iterator> start;
qi::rule<Iterator, event_descriptor()> event_descriptor_;
qi::rule<Iterator, event_entry()> event_entry_;
qi::rule<Iterator, event_entry_qualifier()> event_qualifier;
qi::rule<Iterator, entry_type()> atomic_type;
qi::rule<Iterator, entry_type()> event_type;
qi::rule<Iterator, type_descriptor()> type_descriptor_;
qi::rule<Iterator, oid()> oid_;
};
std::string test = " EVENT 1:sihan { OPTIONAL 123:hassan int4; OPTIONAL 321:hassan2 int4; } ";
int main()
{
typedef lex::lexertl::position_token<std::string::iterator, boost::mpl::vector<boost::uint32_t, std::string> > token_type; //CHANGED
typedef lex::lexertl::actor_lexer<token_type> lexer_type;
typedef tokens<lexer_type>::iterator_type iterator_type;
tokens<lexer_type> token_lexer;
grammar<iterator_type,tokens<lexer_type>::lexer_def> grammar(token_lexer);
std::string::iterator it = test.begin();
iterator_type first = token_lexer.begin(it, test.end());
iterator_type last = token_lexer.end();
bool r;
r = qi::parse(first, last, grammar); //CHANGED
if(r)
;
else
{
std::cout << "parsing failed" << std::endl;
}
}
来源：https://stackoverflow.com/questions/19203490/boost-spirit-parser-lex-qi-getting-the-undocumented-on-success-mechanism-to