谢谢您的快速提示!我刚刚尝试过你的代码,除非我做错了什么......我得到这个输出:Syntax error:abc 8.81 Parsed:-a atoken Syntax error:-b btoken Syntax error:-c ctoken Syntax error:-d dtoken
– G. Civardi 2 小时前 https://stackoverflow.com/questions/16177184/return-type-deduction-of-boost-spirit-expression-made-of-variadic-function-expan/16179565#comment23128636_16179565
好吧,所以,我不能不管它:/
原来有未定义的行为涉及,因为解析器表达式被传递到的方式expandBitwise
和被复制:Boost Proto 表达式模板并不是为了被复制而设计的,因为它们可能包含对临时变量的引用,而临时变量的生命周期在其包含的完整表达式结束时结束。
有关更多背景信息,请参阅讨论2 秒内从零加速到 60 英里/小时! http://boost-spirit.com/home/articles/qi-example/zero-to-60-mph-in-2-seconds/
经过很长一段时间的调整rule_.alias()
and boost::proto::deepcopy
我已经达到以下解决方案(顺便说一句,它根本不再需要辅助函数):
template<typename ...Tail>
void mparse(const std::string& line,Tail& ...tail)
{
auto parser = boost::fusion::fold(
boost::tie(ph::bind(&TStruct::rule_, arg1)(tail)...),
qi::eps(false),
deepcopy_(arg2 | arg1)
);
auto f=begin(line), l=end(line);
if( qi::phrase_parse(f, l, parser, ascii::space ) )
std::cout << "Parsed:" << line << std::endl;
else
std::cout << "Syntax error:" << line << std::endl;
if (f!=l)
std::cout << "Remaining unparsed: '" << std::string(f,l) << "'\n";
}
针对 UB 的保护是deepcopy_()
调用,这是一个简单的多态可调用适配器boost::proto::deepcopy
:
struct DeepCopy
{
template<typename E> struct result { typedef typename boost::proto::result_of::deep_copy<E>::type type; };
template<typename E>
typename result<E>::type
operator()(E const& expr) const {
return boost::proto::deep_copy(expr);
}
};
static const ph::function<DeepCopy> deepcopy_;
使用这段代码,你瞧,输出变成:
Syntax error:abc 8.81
Remaining unparsed: 'abc 8.81'
Parsed:-a atoken
Parsed:-b btoken
Parsed:-c ctoken
Parsed:-d dtoken
Bye
作为奖励,代码现在允许您使用 Spirit 的内置 debug() 功能(取消注释该行):
<-d>
<try>abc 8.81</try>
<fail/>
</-d>
<-c>
<try>abc 8.81</try>
<fail/>
</-c>
<-b>
<try>abc 8.81</try>
<fail/>
</-b>
<-a>
<try>abc 8.81</try>
<fail/>
</-a>
Syntax error:abc 8.81
Remaining unparsed: 'abc 8.81'
测试用
- 提升 1_54_0
- GCC 4.7.2、4.8.x、铿锵 3.2
- 请注意
#define
是重要的。
完整代码
#define BOOST_RESULT_OF_USE_DECLTYPE
#define BOOST_SPIRIT_USE_PHOENIX_V3
#include <boost/fusion/adapted/boost_tuple.hpp>
#include <boost/fusion/include/fold.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
namespace qi = boost::spirit::qi;
namespace ph = boost::phoenix;
namespace ascii = boost::spirit::ascii;
using namespace ph::arg_names;
typedef qi::rule<std::string::const_iterator,ascii::space_type> mrule_t;
typedef qi::rule<std::string::const_iterator,std::string() > wrule_t;
struct TStruct
{
mrule_t rule_;
template<typename T,typename R>
TStruct( T& rVar,const std::string&name, R& rule ) :
rule_( qi::lit(name) >> rule[ ph::ref(rVar) = qi::_1 ] )
{
rule_.name(name);
// debug(rule_);
}
};
struct DeepCopy
{
template<typename E> struct result { typedef typename boost::proto::result_of::deep_copy<E>::type type; };
template<typename E>
typename result<E>::type
operator()(E const& expr) const {
return boost::proto::deep_copy(expr);
}
};
static const ph::function<DeepCopy> deepcopy_;
template<typename ...Tail>
void mparse(const std::string& line,Tail& ...tail)
{
auto parser = boost::fusion::fold(
boost::tie(ph::bind(&TStruct::rule_, arg1)(tail)...),
qi::eps(false),
deepcopy_(arg2 | arg1)
);
auto f=begin(line), l=end(line);
if( qi::phrase_parse(f, l, parser, ascii::space ) )
std::cout << "Parsed:" << line << std::endl;
else
std::cout << "Syntax error:" << line << std::endl;
if (f!=l)
std::cout << "Remaining unparsed: '" << std::string(f,l) << "'\n";
}
int main()
{
wrule_t rword=+~ascii::space;
std::string par1,par2,par3,par4;
TStruct r1( par1, "-a", rword );
TStruct r2( par2, "-b", rword );
TStruct r3( par3, "-c", rword );
TStruct r4( par4, "-d", rword );
mparse("abc 8.81" ,r1,r2,r3,r4);
mparse("-a atoken" ,r1,r2,r3,r4);
mparse("-b btoken" ,r1,r2,r3,r4);
mparse("-c ctoken" ,r1,r2,r3,r4);
mparse("-d dtoken" ,r1,r2,r3,r4);
std::cout << "Bye\n";
}