Hi, I get a compiler error (cannot convert from 'const phoenix::nil_t' to 'int') when using arg2 of a two value closure. arg1 works fine, but not arg2. I don't understand what I have done wrong. Visual Studio 2005 SP1 boost 1.36.0 Anyone got any ideas? Best regards, Anders Dalvander Output: Compiling... SpiritClosureTest.cpp d:\prog\boost_1_36_0\boost\spirit\home\classic\phoenix\operators.hpp(446) : error C2440: '=' : cannot convert from 'const phoenix::nil_t' to 'int' No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called d:\prog\boost_1_36_0\boost\spirit\home\classic\phoenix\operators.hpp(446) : while compiling class template member function 'int &phoenix::binary_operator<TagT,T0,T1>::eval(T0 &,const T1 &)' with [ TagT=phoenix::assign_op, T0=int, T1=phoenix::nil_t ] d:\prog\boost_1_36_0\boost\spirit\home\classic\phoenix\operators.hpp(1017) : see reference to class template instantiation 'phoenix::binary_operator<TagT,T0,T1>' being compiled with [ TagT=phoenix::assign_op, T0=int, T1=phoenix::nil_t ] d:\prog\boost_1_36_0\boost\spirit\home\classic\phoenix\composite.hpp(237) : see reference to class template instantiation 'phoenix::assign_op::result<T0,T1>' being compiled with [ T0=int, T1=phoenix::nil_t ] d:\prog\boost_1_36_0\boost\spirit\home\classic\phoenix\composite.hpp(267) : see reference to class template instantiation 'phoenix::composite2_result<OperationT,TupleT,A,B>' being compiled with [ OperationT=phoenix::assign_op, TupleT=phoenix::tuple<>, A=phoenix::actor<phoenix::closure_member<0,phoenix::closure<int,int,phoenix::nil_t>>>, B=phoenix::actor<phoenix::argument<0>> ] d:\prog\boost_1_36_0\boost\spirit\home\classic\phoenix\actor.hpp(122) : see reference to class template instantiation 'phoenix::composite<OperationT,A,B,C>::result<TupleT>' being compiled with [ OperationT=phoenix::assign_op, A=phoenix::actor<phoenix::closure_member<0,phoenix::closure<int,int,phoenix::nil_t>>>, B=phoenix::actor<phoenix::argument<0>>, C=phoenix::as_actor<phoenix::nil_t>::type, TupleT=phoenix::tuple<> ] d:\prog\boost_1_36_0\boost\spirit\home\classic\phoenix\actor.hpp(133) : see reference to class template instantiation 'phoenix::actor_result<ActorT,TupleT>' being compiled with [ ActorT=phoenix::composite<phoenix::assign_op,phoenix::actor<phoenix::closure_member<0,phoenix::closure<int,int,phoenix::nil_t>>>,phoenix::actor<phoenix::argument<0>>,phoenix::as_actor<phoenix::nil_t>::type>, TupleT=phoenix::tuple<> ] c:\documents and settings\anders\my documents\visual studio 2005\projects\spiritclosuretest\spiritclosuretest\spiritclosuretest.cpp(25) : see reference to class template instantiation 'phoenix::actor<BaseT>' being compiled with [ BaseT=phoenix::composite<phoenix::assign_op,phoenix::actor<phoenix::closure_member<0,phoenix::closure<int,int,phoenix::nil_t>>>,phoenix::actor<phoenix::argument<0>>,phoenix::as_actor<phoenix::nil_t>::type> ] c:\documents and settings\anders\my documents\visual studio 2005\projects\spiritclosuretest\spiritclosuretest\spiritclosuretest.cpp(16) : while compiling class template member function 'my_grammar::definition<ScannerT>::definition(const my_grammar &)' with [ ScannerT=boost::spirit::scanner<> ] d:\prog\boost_1_36_0\boost\spirit\home\classic\core\non_terminal\impl\grammar.ipp(279) : see reference to class template instantiation 'my_grammar::definition<ScannerT>' being compiled with [ ScannerT=boost::spirit::scanner<> ] d:\prog\boost_1_36_0\boost\spirit\home\classic\core\non_terminal\impl\grammar.ipp(298) : see reference to function template instantiation 'void boost::spirit::impl::call_helper<0>::do_<result_t,definition_t,ScannerT>(RT &,DefinitionT &,const ScannerT &)' being compiled with [ ScannerT=boost::spirit::scanner<>, RT=result_t, DefinitionT=definition_t ] d:\prog\boost_1_36_0\boost\spirit\home\classic\core\non_terminal\grammar.hpp(55) : see reference to function template instantiation 'boost::spirit::match<boost::spirit::nil_t> boost::spirit::impl::grammar_parser_parse<0,my_grammar,boost::spirit::parser_context<>,ScannerT>(const boost::spirit::grammar<DerivedT> *,const ScannerT &)' being compiled with [ ScannerT=boost::spirit::scanner<>, DerivedT=my_grammar ] d:\prog\boost_1_36_0\boost\spirit\home\classic\core\non_terminal\grammar.hpp(65) : see reference to function template instantiation 'boost::spirit::match<boost::spirit::nil_t> boost::spirit::grammar<DerivedT>::parse_main<ScannerT>(const ScannerT &) const' being compiled with [ DerivedT=my_grammar, ScannerT=boost::spirit::scanner<> ] d:\prog\boost_1_36_0\boost\spirit\home\classic\core\impl\parser.ipp(30) : see reference to function template instantiation 'boost::spirit::match<boost::spirit::nil_t> boost::spirit::grammar<DerivedT>::parse<boost::spirit::scanner<>>(const ScannerT &) const' being compiled with [ DerivedT=my_grammar, ScannerT=boost::spirit::scanner<> ] d:\prog\boost_1_36_0\boost\spirit\home\classic\core\impl\parser.ipp(47) : see reference to function template instantiation 'boost::spirit::parse_info<IteratorT> boost::spirit::parse<const CharT*,DerivedT>(const IteratorT &,const IteratorT &,const boost::spirit::parser<DerivedT> &)' being compiled with [ IteratorT=const char *, CharT=char, DerivedT=my_grammar ] c:\documents and settings\anders\my documents\visual studio 2005\projects\spiritclosuretest\spiritclosuretest\spiritclosuretest.cpp(54) : see reference to function template instantiation 'boost::spirit::parse_info<IteratorT> boost::spirit::parse<char,DerivedT>(const CharT *,const boost::spirit::parser<DerivedT> &)' being compiled with [ IteratorT=const char *, DerivedT=my_grammar, CharT=char ] Source: #include <boost/spirit.hpp> #include <boost/spirit/phoenix/primitives.hpp> #include <iostream> struct result_closure : boost::spirit::closure<result_closure, int, int> { member1 res1; member2 res2; }; struct my_grammar : boost::spirit::grammar<my_grammar> { template <typename ScannerT> struct definition { explicit definition(const my_grammar& self) { using boost::spirit::ch_p; using boost::spirit::uint_p; using phoenix::var; using phoenix::arg1; using phoenix::arg2; exp = uint_p[exp.res1 = arg1] >> ch_p('-') >> uint_p[exp.res2 = arg1] ; root = exp[var(self.i) = arg2] // compiler error here if using arg2. ; // arg1 works fine though. } boost::spirit::rule<ScannerT, result_closure::context_t> exp; boost::spirit::rule<ScannerT> root; const boost::spirit::rule<ScannerT>& start() const { return root; } }; my_grammar(int& i_) : i(i_) { } int& i; }; int main() { int i; my_grammar g(i); if (parse("1-2", g).full) { std::cout << i << "\n"; } }