我试图简单地解释这个答案中找到的 spirit 解析器:
删除xor运算符和逻辑。我不知道该怎么做，我尝试使用
expr_ = or_.alias();
or_ = (and__ >> "or" >> or_ )[ _val = phx::construct<binop<op_or >>(_1, _2) ] | and_ [ _val = _1 ];
and_ = (not_ >> "and" >> and_) [ _val = phx::construct<binop<op_and>>(_1, _2) ] | not_ [ _val = _1 ];
not_ = ("not" > simple ) [ _val = phx::construct<unop <op_not>>(_1) ] | simple [ _val = _1 ];
对于规则定义，但我收到一条我不理解的神秘编译器消息:
test\test.cpp `boost::spirit::_2' cannot appear in a constant-expression
如果有人能提供一些线索，我将不胜感激。
这是日志:
compiler: Default compiler Building Makefile:
"D:\Dev-Cpp\test\Makefile.win" Executing make... make.exe -f
"D:\Dev-Cpp\test\Makefile.win" all g++.exe -c test.cpp -o test.o
-I"D:/Dev-Cpp/lib/gcc/mingw32/3.4.2/include" -I"D:/Dev-Cpp/include/c++/3.4.2/backward" -I"D:/Dev-Cpp/include/c++/3.4.2/mingw32" -I"D:/Dev-Cpp/include/c++/3.4.2" -I"D:/Dev-Cpp/include"
test.cpp: In constructor `parser<It, Skipper>::parser()':
test.cpp:76: error: `boost::spirit::_1' cannot appear in a
constant-expression test.cpp:76: error: a comma operator cannot
appear in a constant-expression test.cpp:76: error:
`boost::spirit::_2' cannot appear in a constant-expression
test.cpp:76: error: `>>' should be `> >' within a nested template
argument list
test.cpp:77: error: `boost::spirit::_1' cannot appear in a
constant-expression
test.cpp:77: error: a comma operator cannot appear in a
constant-expression test.cpp:77: error: `boost::spirit::_2' cannot
appear in a constant-expression test.cpp:77: error: `>>' should be `>
>' within a nested template argument list
test.cpp:78: error: `boost::spirit::_1' cannot appear in a
constant-expression
test.cpp:78: error: `>>' should be `> >' within a nested template
argument list
test.cpp: In function `int main()': test.cpp:98: error: expected
primary-expression before "auto" test.cpp:98: error: expected `;'
before "auto"
test.cpp:111: error: expected primary-expression before ')' token
test.cpp:111: error: expected `;' before ')' token test.cpp:113:
error: ISO C++ forbids declaration of `f' with no type test.cpp:113:
error: `begin' is not a member of `std' test.cpp:113: error: `input'
undeclared (first use this function) test.cpp:113: error: (Each
undeclared identifier is reported only once for each function it
appears in.) test.cpp:113: error: ISO C++ forbids declaration of `l'
with no type test.cpp:113: error: `end' is not a member of `std'
test.cpp:114: error: `f' cannot appear in a constant-expression
test.cpp:114: error: a function call cannot appear in a
constant-expression test.cpp:114: error: template argument 1 is
invalid test.cpp:114: error: invalid type in declaration before ';'
token
test.cpp:126: error: `f' cannot appear in a constant-expression
test.cpp:126: error: a function call cannot appear in a
constant-expression test.cpp:126: error: template argument 1 is
invalid test.cpp:126: error: ISO C++ forbids declaration of `e' with
no type
test.cpp:128: error: expected primary-expression before '(' token
test.cpp:128: error: `first' has not been declared test.cpp:128:
error: request for member of non-aggregate type before ',' token
test.cpp:128: error: `last' has not been declared test.cpp:128:
error: request for member of non-aggregate type before ')' token
D:/Dev-Cpp/include/c++/3.4.2/bits/stl_iterator_base_types.h: At
global scope:
D:/Dev-Cpp/include/c++/3.4.2/bits/stl_iterator_base_types.h: In
instantiation of `std::iterator_traits<int>':
D:/Dev-Cpp/include/boost/detail/iterator.hpp:83: instantiated from
`boost::detail::iterator_traits<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:509: instantiated from
`boost::InputIterator<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:545: instantiated from
`boost::ForwardIterator<int>'
D:/Dev-Cpp/include/boost/concept/detail/has_constraints.hpp:42:
instantiated from
`boost::concepts::not_satisfied<boost::ForwardIterator<int> >'
D:/Dev-Cpp/include/boost/mpl/if.hpp:67: instantiated from
`boost::mpl::if_<boost::concepts::not_satisfied<boost::ForwardIterator<int>
>, boost::concepts::constraint<boost::ForwardIterator<int> >, boost::concepts::requirement<boost::concepts::failed************boost::ForwardIterator<int>::************>
>' D:/Dev-Cpp/include/boost/concept/detail/general.hpp:56: instantiated from `boost::concepts::requirement_<void
(*)(boost::ForwardIterator<int>)>'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:149: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, boost::spirit::qi::skip_flag::enum_type,
Attr&) [with Iterator = int, Expr = bool, Skipper =
boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >, 0l>, Attr =
boost::variant<var, boost::recursive_wrapper<unop<op_not> >,
boost::recursive_wrapper<binop<op_and> >,
boost::recursive_wrapper<binop<op_or> >,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_>]'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:197: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, Attr&) [with Iterator = int, Expr = bool,
Skipper = boost::spirit::standard::space_type, Attr = expr]'
test.cpp:119: instantiated from here
D:/Dev-Cpp/include/c++/3.4.2/bits/stl_iterator_base_types.h:129:
error: `int' is not a class, struct, or union type
D:/Dev-Cpp/include/c++/3.4.2/bits/stl_iterator_base_types.h:130:
error: `int' is not a class, struct, or union type
D:/Dev-Cpp/include/c++/3.4.2/bits/stl_iterator_base_types.h:131:
error: `int' is not a class, struct, or union type
D:/Dev-Cpp/include/c++/3.4.2/bits/stl_iterator_base_types.h:132:
error: `int' is not a class, struct, or union type
D:/Dev-Cpp/include/c++/3.4.2/bits/stl_iterator_base_types.h:133:
error: `int' is not a class, struct, or union type
D:/Dev-Cpp/include/boost/concept_check.hpp: In instantiation of
`boost::InputIterator<int>':
D:/Dev-Cpp/include/boost/concept_check.hpp:545: instantiated from
`boost::ForwardIterator<int>'
D:/Dev-Cpp/include/boost/concept/detail/has_constraints.hpp:42:
instantiated from
`boost::concepts::not_satisfied<boost::ForwardIterator<int> >'
D:/Dev-Cpp/include/boost/mpl/if.hpp:67: instantiated from
`boost::mpl::if_<boost::concepts::not_satisfied<boost::ForwardIterator<int>
>, boost::concepts::constraint<boost::ForwardIterator<int> >, boost::concepts::requirement<boost::concepts::failed************boost::ForwardIterator<int>::************>
>' D:/Dev-Cpp/include/boost/concept/detail/general.hpp:56: instantiated from `boost::concepts::requirement_<void
(*)(boost::ForwardIterator<int>)>'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:149: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, boost::spirit::qi::skip_flag::enum_type,
Attr&) [with Iterator = int, Expr = bool, Skipper =
boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >, 0l>, Attr =
boost::variant<var, boost::recursive_wrapper<unop<op_not> >,
boost::recursive_wrapper<binop<op_and> >,
boost::recursive_wrapper<binop<op_or> >,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_>]'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:197: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, Attr&) [with Iterator = int, Expr = bool,
Skipper = boost::spirit::standard::space_type, Attr = expr]'
test.cpp:119: instantiated from here
D:/Dev-Cpp/include/boost/concept_check.hpp:509: error: no type named
`value_type' in `struct boost::detail::iterator_traits<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:510: error: no type named
`difference_type' in `struct boost::detail::iterator_traits<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:511: error: no type named
`reference' in `struct boost::detail::iterator_traits<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:512: error: no type named
`pointer' in `struct boost::detail::iterator_traits<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:513: error: no type named
`iterator_category' in `struct boost::detail::iterator_traits<int>'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp: In function `bool
boost::spirit::qi::phrase_parse(Iterator&, Iterator, const Expr&,
const Skipper&, boost::spirit::qi::skip_flag::enum_type, Attr&) [with
Iterator = int, Expr = bool, Skipper =
boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >, 0l>, Attr =
boost::variant<var, boost::recursive_wrapper<unop<op_not> >,
boost::recursive_wrapper<binop<op_and> >,
boost::recursive_wrapper<binop<op_or> >,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_>]':
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:197: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, Attr&) [with Iterator = int, Expr = bool,
Skipper = boost::spirit::standard::space_type, Attr = expr]'
test.cpp:119: instantiated from here
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:155: error:
conversion from
`mpl_::failed************(boost::spirit::qi::phrase_parse(Iterator&,
Iterator, const Expr&, const Skipper&,
boost::spirit::qi::skip_flag::enum_type, Attr&) [with Iterator = int,
Expr = bool, Skipper =
boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >, 0l>, Attr =
boost::variant<var, boost::recursive_wrapper<unop<op_not> >,
boost::recursive_wrapper<binop<op_and> >,
boost::recursive_wrapper<binop<op_or> >,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_,
boost::detail::variant::void_>]::error_invalid_expression::************)(bool)'
to non-scalar type `mpl_::assert< false>' requested
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:155: error:
enumerator value for `mpl_assertion_in_line_155' not integer constant
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:197: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, Attr&) [with Iterator = int, Expr = bool,
Skipper = boost::spirit::standard::space_type, Attr = expr]'
test.cpp:119: instantiated from here
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:164: error: request
for member `parse' in `boost::spirit::compile [with Domain =
boost::spirit::qi::domain, Expr = bool](((const bool&)(+expr)))',
which is of non-class type `bool'
D:/Dev-Cpp/include/boost/concept_check.hpp: In destructor
`boost::ForwardIterator<TT>::~ForwardIterator() [with TT = int]':
D:/Dev-Cpp/include/boost/concept/detail/general.hpp:38:
instantiated from `static void
boost::concepts::requirement<boost::concepts::failed************Model::************>::failed()
[with Model = boost::ForwardIterator<int>]'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:149: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, boost::spirit::qi::skip_flag::enum_type,
Attr&) [with Iterator = int, Expr = bool, Skipper =
boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >, 0l>, Attr =
boost::variant<var, boost::recursive_wrapper<unop<op_not> >,
boost::recursive_wrapper<binop<op_and> >,
boost::recursive_wrapper<binop<op_or> >,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_>]'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:197: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, Attr&) [with Iterator = int, Expr = bool,
Skipper = boost::spirit::standard::space_type, Attr = expr]'
test.cpp:119: instantiated from here
D:/Dev-Cpp/include/boost/concept_check.hpp:548: error: no type named
`iterator_category' in `struct boost::ForwardIterator<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:548: error: `failed' is
not a member of `<declaration error>'
D:/Dev-Cpp/include/boost/concept_check.hpp:553: error: no type named
`reference' in `struct boost::InputIterator<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:554: error: no type named
`reference' in `struct boost::InputIterator<int>'
D:/Dev-Cpp/include/boost/spirit/home/qi/char/char_parser.hpp: In
member function `bool boost::spirit::qi::char_parser<Derived, Char,
Attr>::parse(Iterator&, const Iterator&, Context&, const Skipper&,
Attribute&) const [with Iterator = int, Context = const
boost::spirit::unused_type, Skipper = boost::spirit::unused_type,
Attribute = const boost::spirit::unused_type, Derived =
boost::spirit::qi::char_class<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >, Char = char, Attr =
char]': D:/Dev-Cpp/include/boost/spirit/home/qi/skip_over.hpp:27:
instantiated from `void boost::spirit::qi::skip_over(Iterator&, const
Iterator&, const T&) [with Iterator = int, T =
boost::spirit::qi::char_class<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >]'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:169: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, boost::spirit::qi::skip_flag::enum_type,
Attr&) [with Iterator = int, Expr = bool, Skipper =
boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >, 0l>, Attr =
boost::variant<var, boost::recursive_wrapper<unop<op_not> >,
boost::recursive_wrapper<binop<op_and> >,
boost::recursive_wrapper<binop<op_or> >,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_>]'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:197: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, Attr&) [with Iterator = int, Expr = bool,
Skipper = boost::spirit::standard::space_type, Attr = expr]'
test.cpp:119: instantiated from here
D:/Dev-Cpp/include/boost/spirit/home/qi/char/char_parser.hpp:68:
error: invalid type argument of `unary *'
D:/Dev-Cpp/include/boost/spirit/home/qi/char/char_parser.hpp:70:
error: invalid type argument of `unary *'
D:/Dev-Cpp/include/boost/concept_check.hpp: In destructor
`boost::InputIterator<TT>::~InputIterator() [with TT = int]':
D:/Dev-Cpp/include/boost/concept_check.hpp:547: instantiated from
`boost::ForwardIterator<TT>::~ForwardIterator() [with TT = int]'
D:/Dev-Cpp/include/boost/concept/detail/general.hpp:38:
instantiated from `static void
boost::concepts::requirement<boost::concepts::failed************Model::************>::failed()
[with Model = boost::ForwardIterator<int>]'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:149: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, boost::spirit::qi::skip_flag::enum_type,
Attr&) [with Iterator = int, Expr = bool, Skipper =
boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space,
boost::spirit::char_encoding::standard> >, 0l>, Attr =
boost::variant<var, boost::recursive_wrapper<unop<op_not> >,
boost::recursive_wrapper<binop<op_and> >,
boost::recursive_wrapper<binop<op_or> >,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_,
boost::detail::variant::void_, boost::detail::variant::void_>]'
D:/Dev-Cpp/include/boost/spirit/home/qi/parse.hpp:197: instantiated
from `bool boost::spirit::qi::phrase_parse(Iterator&, Iterator, const
Expr&, const Skipper&, Attr&) [with Iterator = int, Expr = bool,
Skipper = boost::spirit::standard::space_type, Attr = expr]'
test.cpp:119: instantiated from here
D:/Dev-Cpp/include/boost/concept_check.hpp:517: error: no type named
`difference_type' in `struct boost::detail::iterator_traits<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:517: error: `failed' is
not a member of `<declaration error>'
D:/Dev-Cpp/include/boost/concept_check.hpp:518: error: no type named
`iterator_category' in `struct boost::detail::iterator_traits<int>'
D:/Dev-Cpp/include/boost/concept_check.hpp:518: error: `failed' is
not a member of `<declaration error>'
D:/Dev-Cpp/include/boost/concept_check.hpp:521: error: invalid type
argument of `unary *'
make.exe: *** [test.o] Error 1
Execution terminated
最佳答案
您不小心将 and_ 输入为 and__。
将 and__ 更改为 and_ 将使其编译。
这是一个更简洁的版本，删除了现在不需要的与xor相关的声明:
编辑 对于不了解 auto、decltype、正确模板解析的旧编译器也进行“反向移植”(>> 与 >>)等):
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <boost/variant/recursive_wrapper.hpp>
namespace qi = boost::spirit::qi;
namespace phx = boost::phoenix;
struct op_or {};
struct op_and {};
struct op_not {};
typedef std::string var;
template <typename tag> struct binop;
template <typename tag> struct unop;
typedef boost::variant<var,
boost::recursive_wrapper<unop <op_not> >,
boost::recursive_wrapper<binop<op_and> >,
boost::recursive_wrapper<binop<op_or> >
> expr;
template <typename tag> struct binop
{
explicit binop(const expr& l, const expr& r) : oper1(l), oper2(r) { }
expr oper1, oper2;
};
template <typename tag> struct unop
{
explicit unop(const expr& o) : oper1(o) { }
expr oper1;
};
struct printer : boost::static_visitor<void>
{
printer(std::ostream& os) : _os(os) {}
std::ostream& _os;
//
void operator()(const var& v) const { _os << v; }
void operator()(const binop<op_and>& b) const { print(" & ", b.oper1, b.oper2); }
void operator()(const binop<op_or >& b) const { print(" | ", b.oper1, b.oper2); }
void print(const std::string& op, const expr& l, const expr& r) const
{
_os << "(";
boost::apply_visitor(*this, l);
_os << op;
boost::apply_visitor(*this, r);
_os << ")";
}
void operator()(const unop<op_not>& u) const
{
_os << "(";
_os << "!";
boost::apply_visitor(*this, u.oper1);
_os << ")";
}
};
std::ostream& operator<<(std::ostream& os, const expr& e)
{ boost::apply_visitor(printer(os), e); return os; }
template <typename It, typename Skipper = qi::space_type>
struct parser : qi::grammar<It, expr(), Skipper>
{
parser() : parser::base_type(expr_)
{
using namespace qi;
expr_ = or_.alias();
or_ = (and_ >> "or" >> or_ ) [ _val = phx::construct<binop<op_or > >(_1, _2) ] | and_ [ _val = _1 ];
and_ = (not_ >> "and" >> and_) [ _val = phx::construct<binop<op_and> >(_1, _2) ] | not_ [ _val = _1 ];
not_ = ("not" > simple ) [ _val = phx::construct<unop <op_not> >(_1) ] | simple [ _val = _1 ];
simple = (('(' > expr_ > ')') | var_);
var_ = qi::lexeme[ +alpha ];
BOOST_SPIRIT_DEBUG_NODE(expr_);
BOOST_SPIRIT_DEBUG_NODE(or_);
BOOST_SPIRIT_DEBUG_NODE(and_);
BOOST_SPIRIT_DEBUG_NODE(not_);
BOOST_SPIRIT_DEBUG_NODE(simple);
BOOST_SPIRIT_DEBUG_NODE(var_);
}
private:
qi::rule<It, var() , Skipper> var_;
qi::rule<It, expr(), Skipper> not_, and_, or_, simple, expr_;
};
int main()
{
const std::string inputs[] = {
// From the OP:
std::string("(a and b) or ((c and d) or (a and b));"),
std::string("a and b or (c and d or a and b);"),
/// Simpler tests:
std::string("a and b;"),
std::string("a or b;"),
std::string("a or b;"),
std::string("not a;"),
std::string("not a and b;"),
std::string("not (a and b);"),
std::string("a or b or c;"),
std::string("") // marker
};
for (const std::string *i = inputs; !i->empty(); ++i)
{
typedef std::string::const_iterator It;
It f(i->begin()), l(i->end());
parser<It> p;
try
{
expr result;
bool ok = qi::phrase_parse(f,l,p > ';',qi::space,result);
if (!ok)
std::cerr << "invalid input\n";
else
std::cout << "result: " << result << "\n";
} catch (const qi::expectation_failure<It>& e)
{
std::cerr << "expectation_failure at '" << std::string(e.first, e.last) << "'\n";
}
if (f!=l) std::cerr << "unparsed: '" << std::string(f,l) << "'\n";
}
return 0;
}
运行此示例的输出是
result: ((a & b) | ((c & d) | (a & b)))
result: ((a & b) | ((c & d) | (a & b)))
result: (a & b)
result: (a | b)
result: (a | b)
result: (!a)
result: ((!a) & b)
result: (!(a & b))
result: (a | (b | c))
关于c++ - 使用 Boost 的 bool 表达式，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12587148/