struct Parser: public qi::grammar<Iterator, utree()>
{
template <typename Tokens>
Parser(const Tokens &toks):
Parser::base_type(expression)
{
chain = +(
(
toks.symbol
[
_val = construct<utree::list_type>()
// some code here
]
| (
factor >>
+(
toks.arrow >> factor
| toks.dot >> factor
)
)
[
_val = construct<utree::list_type>()
// some code here
]
) >> toks.assign
);
expression = factor
| (chain >> factor) [ _val = ternary(_1, _2) ]
;
}
rule<Iterator, utree::list_type()> chain;
rule<Iterator, utree()> expression, factor, test;
};
注意:如果你想你應該能夠做同樣沒有額外的規則定義(使用qi::attr_cast<>
,qi::as<>
例如),但我懷疑這將是可讀/維護。
PS。類似的點可以從calc_utree_naive.cpp
中拿走,它必然會使用比使用SA的calc_utree_ast.cpp
版本更明確的規則屬性類型。
下面是完整的,編譯版本,與一些在線筆記註釋:
// #define BOOST_SPIRIT_USE_PHOENIX_V3
// #define BOOST_RESULT_OF_USE_DECLTYPE
#include <algorithm>
#include <string>
#include <boost/spirit/include/lex_lexertl.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/support_utree.hpp>
#include <boost/spirit/include/phoenix_function.hpp>
#include <boost/spirit/include/phoenix_object.hpp>
#include <boost/spirit/include/phoenix_stl.hpp>
namespace lex = boost::spirit::lex;
namespace qi = boost::spirit::qi;
namespace spirit = boost::spirit;
namespace phx = boost::phoenix;
using lex::token_def;
using qi::rule;
using qi::_1;
using qi::_2;
using qi::_val;
using spirit::utree;
using phx::construct;
// base iterator type
typedef std::string::iterator BaseIteratorT;
// token type
typedef lex::lexertl::token<BaseIteratorT, boost::mpl::vector</*double, int, */std::string> > TokenT;
// lexer type
typedef lex::lexertl::actor_lexer<TokenT> LexerT;
template <typename LexerT>
struct Tokens: public lex::lexer<LexerT>
{
Tokens()
{
using lex::_pass;
using lex::pass_flags;
// literals
symbol = "[a-zA-Z_?](\\w|\\?)*|@(\\w|\\?)+";
arrow = "->";
dot = '.';
assign = "=";
// literal rules
this->self += symbol;
this->self += arrow;
this->self += dot;
this->self += assign;
}
~Tokens() {}
// literal tokens
token_def<std::string> symbol;
token_def<> arrow, dot; // HINT: lex::omit here?
/*
*^Otherwise, expect these to be all exposed as Qi attributes as well, so
* _1, _2, _3, _4 a bit more than you'd expect
*/
token_def<lex::omit> assign;
};
struct ternaryImpl
{
template <typename Expr1Type, typename Expr2Type>
struct result { typedef utree type; };
template <typename Expr1Type, typename Expr2Type>
utree operator()(Expr1Type &vec, Expr2Type &operand) const {
utree ret;
for (typename Expr1Type::iterator it = vec.begin(); it != vec.end(); ++it) {
// some code
ret = *it;
// more code
}
// some code here
return ret;
}
};
phx::function<ternaryImpl> ternary = ternaryImpl();
template <typename Iterator>
struct Parser: public qi::grammar<Iterator, utree()>
{
template <typename Tokens>
Parser(const Tokens &toks):
Parser::base_type(expression)
{
chain = +(
(
toks.symbol
[
_val = construct<utree::list_type>()
// some code here
]
| (
factor >>
+(
toks.arrow >> factor
| toks.dot >> factor
)
)
[
_val = construct<utree::list_type>()
// some code here
]
) >> toks.assign
);
expression = factor
| (chain >> factor) [ _val = ternary(_1, _2) ]
;
}
rule<Iterator, utree::list_type()> chain;
rule<Iterator, utree()> expression, factor, test;
};
int main()
{
typedef Tokens<LexerT>::iterator_type IteratorT;
Tokens<LexerT> l;
Parser<IteratorT> p(l);
}
謝謝!這對我有效。 – 2012-07-17 17:45:34