During parsing I have a few attributes that I need to set in semantic action only ( as they are derived from data being parsed and I want to avoid global variables and dependency on BOOST_FUSION_ADAPT_STRUCT as well as my code should be generic so that I can reuse it for multiple types). If I use more than one variable passed into qi::phrase_parse I get very long list of compilation errors. I need a help badly :-)
#define BOOST_RESULT_OF_USE_DECLTYPE
#define BOOST_SPIRIT_USE_PHOENIX_V3
#include <boost/function.hpp>
#include <boost/phoenix/fusion.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/spirit/include/qi.hpp>
#include <iostream>
#include <string>
#include <climits>
namespace qi = boost::spirit::qi;
namespace ph = boost::phoenix;
namespace ascii = boost::spirit::ascii;
int main( int argc, char**argv )
{
bool rc;
std::string input("");
//Test case 1 works fine
{
auto iter( input.begin() );
auto last( input.end() );
int val1=33;
rc = qi::phrase_parse( iter, last, qi::eps[ qi::_val=11 ] ,
ascii::space, val1 ) && iter==last;
if( rc )
std::cout << "val1=" << val1 << std::endl;
}
//Test case 2 does not compile
{
auto iter( input.begin() );
auto last( input.end() );
int val1=33;
int val2=0;
rc = qi::phrase_parse( iter, last,
qi::eps[ ph::at_c<0>(qi::_val)=1,ph::at_c<1>(qi::_val)=2 ],
ascii::space, val1,val2 ) && iter==last;
if( rc )
std::cout << "val1=" << val1 <<
" val2=" << val2 << std::endl;
}
//Test case 3 works fine
{
auto iter( input.begin() );
auto last( input.end() );
int val1=33;
int val2=0;
rc = qi::phrase_parse( iter, last,
qi::attr(1)>>qi::attr(2),
ascii::space, val1,val2 ) && iter==last;
if( rc )
std::cout << "val1=" << val1 <<
" val2=" << val2 << std::endl;
}
return 0;
}
I took the "customized" my_phrase_parse from cv_and_he but it breaks compilation on the full test case that I want to get running:
template<typename T,typename R>
void testParser( R rule )
{
for ( const auto input : std::vector< std::string >{ "5 1.0 2.0 3.0 4.0 5.0", "1 1.0", "0" , "", "2 3 ab" } )
{
bool rc;
T maxValue;
T minValue;
auto iter( input.begin() );
auto last( input.end() );
std::vector< T > v;
rc = my_phrase_parse( iter, last,
qi::eps[
ph::at_c<0>(qi::_val)=std::numeric_limits<T>::max(),
ph::at_c<1>(qi::_val)=std::numeric_limits<T>::min()
]
>> -( qi::omit[ qi::int_]
>> *rule[ ph::if_(ph::at_c<0>(qi::_val)>qi::_1)[ ph::at_c<0>(qi::_val)=qi::_1 ],
ph::if_(ph::at_c<1>(qi::_val)<qi::_1)[ ph::at_c<1>(qi::_val)=qi::_1 ]
] )
,ascii::space, minValue, maxValue,v ) && iter==last;
std::cout << ( rc ? "ok :`" : "err:`" ) << input << "` -> ";
if( rc )
{
std::cout << "min=" << minValue << " max=" << maxValue << "\t";
std::copy( v.begin(), v.end(), std::ostream_iterator<T>( std::cout," " ));
}
else
std::cout << *iter;
std::cout << std::endl;
}
}
...
testParser<double>( qi::double_ );
The Phoenix placeholders that Spirit uses allow you to manipulate important information from a rule's Context. When you use them directly in an expression in a call to parse or phrase_parse there is no rule, and thus no context. Before version Boost 1.47.0 that didn't work, and in order to make this behaviour consistent a fix was applied to the single argument versions of those functions, but apparently not to the variadic ones.
One way to sidestep this problem is creating a rule that has as attribute a fusion::vector of references to the types you use in your call to phrase_parse.
Edit: removed "my_phrase_parse" since I'm not confident that it is correct
#define BOOST_RESULT_OF_USE_DECLTYPE
#define BOOST_SPIRIT_USE_PHOENIX_V3
#include <boost/function.hpp>
#include <boost/phoenix/fusion.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/spirit/include/qi.hpp>
#include <iostream>
#include <string>
namespace qi = boost::spirit::qi;
namespace ph = boost::phoenix;
namespace ascii = boost::spirit::ascii;
namespace fusion = boost::fusion;
int main( int argc, char**argv )
{
bool rc;
std::string input("");
//Test case works fine
{
auto iter( input.begin() );
auto last( input.end() );
int val1=33;
rc = qi::phrase_parse( iter, last, qi::eps[ qi::_val=11 ] ,
ascii::space, val1 ) && iter==last;
if( rc )
std::cout << "val1=" << val1 << std::endl;
}
//You can use a rule
{
auto iter( input.begin() );
auto last( input.end() );
int val1=33;
int val2=0;
qi::rule<decltype(iter),fusion::vector<int&, int&>(),ascii::space_type> parser=qi::eps[ ph::at_c<0>(qi::_val)=1,ph::at_c<1>(qi::_val)=2 ];
rc = qi::phrase_parse( iter, last,
parser,
ascii::space, val1,val2 ) && iter==last;
if( rc )
std::cout << "val1=" << val1 <<
" val2=" << val2 << std::endl;
}
return 0;
}
Edit 2: Added another way to approach the problem you want to solve in your edit
#define BOOST_RESULT_OF_USE_DECLTYPE
#define BOOST_SPIRIT_USE_PHOENIX_V3
#include <boost/spirit/include/qi_core.hpp>
#include <boost/spirit/include/qi_omit.hpp>
#include <iostream>
#include <string>
#include <climits>
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
template <typename T>
struct min_max_set
{
min_max_set():min(std::numeric_limits<T>::max()),max(std::numeric_limits<T>::min()),set(){}
T min;
T max;
std::vector<T> set;
};
namespace boost{ namespace spirit { namespace traits
{
template <typename T>
struct is_container<min_max_set<T>>
: boost::mpl::true_
{};
template <typename T>
struct container_value<min_max_set<T>>
{
typedef T type;
};
template <typename T>
struct push_back_container<min_max_set<T>,T>
{
static bool call(min_max_set<T>& cont, const T& val)
{
if(cont.min>val)
cont.min=val;
if(cont.max<val)
cont.max=val;
cont.set.push_back(val);
return true;
}
};
}}}
template<typename T,typename R>
void testParser( R rule )
{
for ( const auto input : std::vector< std::string >{ "5 1.0 2.0 3.0 4.0 5.0", "1 1.0", "0" , "", "2 3 ab" } )
{
bool rc;
auto iter( input.begin() );
auto last( input.end() );
min_max_set<T> accum;
rc = qi::phrase_parse( iter, last,
qi::omit[qi::int_] >> *rule
,ascii::space, accum ) && iter==last;
std::cout << ( rc ? "ok :`" : "err:`" ) << input << "` -> ";
if( rc )
{
std::cout << "min=" << accum.min << " max=" << accum.max << "\t";
std::copy( accum.set.begin(), accum.set.end(), std::ostream_iterator<T>( std::cout," " ));
}
else
std::cout << *iter;
std::cout << std::endl;
}
}
int main( int argc, char**argv )
{
testParser<double>(qi::double_);
return 0;
}