是的，phx::bind 和 phx::function 将默认采用它们的包装器可调用对象的值。但是。
假设[1]，你有一个像这样的错误处理程序......极简示例：
template <typename=void> struct my_error_handler {
my_error_handler() = default;
my_error_handler(my_error_handler const&) = delete;
template<typename...> struct result { typedef void type; };
template<typename... T> void operator()(T&&...) const {
std::cerr << "my_error_handler invoked " << proof++ << "\n";
}
mutable int proof = 0;
};
（如您所见，我明确地将其设为不可复制，以确保编译器不会在我背后默默地生成代码。）
现在，我不确定这是否是您不小心错过的组合，但是：
on_error<fail>(function, phx::bind(phx::ref(err_handler), L"Error: Expecting ", _4, _3));
on_error<fail>(start, phx::bind(phx::ref(err_handler), L"Error: Expecting ", _4, _3));
on_error<fail>(gr_instruction, phx::bind(phx::ref(err_handler), L"Error: Expecting ", _4, _3));
效果很好，就像
auto ll = phx::bind(phx::ref(err_handler), L"Error: Expecting ", _4, _3);
on_error<fail>(function, ll);
on_error<fail>(start, ll);
on_error<fail>(gr_instruction, ll);
注意，因为bind 需要一个引用，我们需要确保err_handler 的生命周期匹配（或超过）解析器的生命周期，所以我将err_handler 设为解析器类的成员。
当我通过它输入失败时，我的程序将能够打印proof 的调用my_error_handler：
std::cout << "The 'proof' in the err_handler instance is: " << p.err_handler.proof << "\n";
与往常一样，一个完全集成的示例程序：
#define BOOST_SPIRIT_USE_PHOENIX_V3
//#define BOOST_SPIRIT_DEBUG
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
namespace qi = boost::spirit::qi;
namespace phx = boost::phoenix;
namespace asmast
{
typedef std::string label;
}
template <typename=void> struct my_error_handler {
my_error_handler() = default;
my_error_handler(my_error_handler const&) = delete;
template<typename...> struct result { typedef void type; };
template<typename... T> void operator()(T&&...) const {
std::cerr << "my_error_handler invoked " << proof++ << "\n";
}
mutable int proof = 0;
};
template <typename It, typename Skipper = qi::blank_type>
struct parser : qi::grammar<It, Skipper>
{
parser() :
parser::base_type(start)
{
using namespace qi;
start = lexeme["Func" >> !(alnum | '_')] > function;
function = gr_identifier
>> "{"
>> -(
gr_instruction
| gr_label
//| gr_vardecl
//| gr_paramdecl
) % eol
> "}";
gr_instruction_names.add("Mov", unused);
gr_instruction_names.add("Push", unused);
gr_instruction_names.add("Exit", unused);
gr_instruction = lexeme [ gr_instruction_names >> !(alnum|"_") ] > gr_operands;
gr_operands = -(gr_operand % ',');
gr_identifier = lexeme [ alpha >> *(alnum | '_') ];
gr_operand = gr_identifier | gr_string;
gr_string = lexeme [ '"' >> *("\"\"" | ~char_("\"")) >> '"' ];
gr_newline = +( char_('\r')
|char_('\n')
);
gr_label = gr_identifier >> ':' > gr_newline;
#if 1
on_error<fail>(function, phx::bind(phx::ref(err_handler), L"Error: Expecting ", _4, _3));
on_error<fail>(start, phx::bind(phx::ref(err_handler), L"Error: Expecting ", _4, _3));
on_error<fail>(gr_instruction, phx::bind(phx::ref(err_handler), L"Error: Expecting ", _4, _3));
#else
auto ll = phx::bind(phx::ref(err_handler), L"Error: Expecting ", _4, _3);
on_error<fail>(function, ll);
on_error<fail>(start, ll);
on_error<fail>(gr_instruction, ll);
#endif
// more on_error<fail>s...
BOOST_SPIRIT_DEBUG_NODES((start)(function)(gr_instruction)(gr_operands)(gr_identifier)(gr_operand)(gr_string));
}
my_error_handler<> err_handler;
private:
qi::symbols<char, qi::unused_type> gr_instruction_names;
qi::rule<It, Skipper> start, function, gr_instruction, gr_operands, gr_operand, gr_string;
qi::rule<It, qi::unused_type()> gr_newline;
qi::rule<It, asmast::label(), Skipper> gr_label, gr_identifier;
};
int main()
{
typedef boost::spirit::istream_iterator It;
std::cin.unsetf(std::ios::skipws);
It f(std::cin), l;
parser<It, qi::blank_type> p;
try
{
bool ok = qi::phrase_parse(f,l,p,qi::blank);
if (ok) std::cout << "parse success\n";
else std::cerr << "parse failed: '" << std::string(f,l) << "'\n";
if (f!=l) std::cerr << "trailing unparsed: '" << std::string(f,l) << "'\n";
std::cout << "The 'proof' in the err_handler instance is: " << p.err_handler.proof << "\n";
return ok;
} catch(const qi::expectation_failure<It>& e)
{
std::string frag(e.first, e.last);
std::cerr << e.what() << "'" << frag << "'\n";
}
return false;
}
当输入输入时
Func Ident{
Mov name, "hello"
Push 5
Exit
}
打印（作为第一行/最后一行）
my_error_handler invoked 0
my_error_handler invoked 1
...
The 'proof' in the err_handler instance is: 2
[1]这不是我第一次不得不想象相关代码