如何引用符号表中的值?

很多事情需要简化。

• 为什么当你使用语义操作时，会调整属性数据？(见振奋精神："语义行为是邪恶的"？
• 使用船长时，跳过空格要优雅得多。跳过词法中的空格在逻辑上也是矛盾的(请参阅提升精神船长问题(

• 特别是，这里跳过空格：

  line_attribute_vec_rule = (line_attribute_rule % *qi::blank) > qi::eoi;
  

  完全无能为力(因为空白已经被跳过了，*qi::blank永远不会匹配任何字符(。整个事情简化为+line_attribute_rule.

  line_attribute_vec_rule = +line_attribute_rule > qi::eoi;
  

回复：您的答案

实际上，您可以在规则中使用更多状态。相反，我会简化 AST 以支持您的案例。说：

struct AttrDef {
std::string word;
std::pair<int,int> range;
};
struct AttributeData {
AttrDef def;
int value;
bool is_valid() const {
return std::minmax({value, def.range.first, def.range.second}) == def.range;
}
};
BOOST_FUSION_ADAPT_STRUCT(AttributeData, def, value)

现在，single_attribute_grammar不会在乎跳过，就像：

using attr_defs = qi::symbols<char, AttrDef>;
template <typename Iterator>
struct single_attribute_grammar : public qi::grammar<Iterator, AttributeData()> {
single_attribute_grammar(const attr_defs &defs)
: single_attribute_grammar::base_type(start) 
{
using namespace qi;
attribute_data = defs >> int_;
start         %= attribute_data [ _pass = is_valid_(_1) ];
BOOST_SPIRIT_DEBUG_NODES((attribute_data));
}
private:
phx::function<std::function<bool(AttributeData const&)> > is_valid_ {&AttributeData::is_valid};
qi::rule<Iterator, AttributeData()> attribute_data;
qi::rule<Iterator, AttributeData()> start;
};

如您所见，没有状态，因为我没有使用eps.没错，我直面我自己的指导方针("避免语义操作"(，原因很简单，它避免了显式状态(而是使用现有的qi::_pass(。

在 main 中做了很多简化(特别是使用boost::spirit::istream_iterator而不是自己的多通道适应(，我会得出这个结论：

住在科里鲁

//#define BOOST_SPIRIT_DEBUG
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/spirit/include/classic_position_iterator.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/io.hpp>
#include <iomanip>
namespace qi      = boost::spirit::qi;
namespace phx     = boost::phoenix;
struct AttrDef {
std::string word;
std::pair<int,int> range;
};
struct AttributeData {
AttrDef def;
int value;
bool is_valid() const {
return std::minmax({value, def.range.first, def.range.second}) == def.range;
}
};
BOOST_FUSION_ADAPT_STRUCT(AttributeData, def, value)
static inline std::ostream& operator<<(std::ostream& os, const AttrDef& def) {
return os << "AttrDef(" << def.word << ", " << def.range.first << ", " << def.range.second << ")";
}
using attr_defs = qi::symbols<char, AttrDef>;
template <typename Iterator>
struct single_attribute_grammar : public qi::grammar<Iterator, AttributeData()> {
single_attribute_grammar(const attr_defs &defs)
: single_attribute_grammar::base_type(start) 
{
using namespace qi;
attribute_data = defs >> int_;
start         %= attribute_data [ _pass = is_valid_(_1) ];
BOOST_SPIRIT_DEBUG_NODES((attribute_data));
}
private:
phx::function<std::function<bool(AttributeData const&)> > is_valid_ {&AttributeData::is_valid};
qi::rule<Iterator, AttributeData()> attribute_data;
qi::rule<Iterator, AttributeData()> start;
};
using AttributeVariant = boost::variant<AttributeData>;
template <typename Iterator>
class all_attributes_grammar : public qi::grammar<Iterator, std::vector<AttributeVariant>(), qi::blank_type>
{
public:
all_attributes_grammar(const attr_defs &defs)
: all_attributes_grammar::base_type(line_attribute_vec_rule),
sag(defs)
{
line_attribute_rule = (
sag
);
line_attribute_vec_rule = +line_attribute_rule > qi::eoi;
BOOST_SPIRIT_DEBUG_NODES((line_attribute_rule)(line_attribute_vec_rule));
}
private:
single_attribute_grammar<Iterator> sag;
qi::rule<Iterator, AttributeVariant()>                              line_attribute_rule;
qi::rule<Iterator, std::vector<AttributeVariant>(), qi::blank_type> line_attribute_vec_rule;
};
int main() {
constexpr bool fail = false, succeed = true;
struct _ { bool expect; std::string data; } const tests[] = {
{ succeed, "N100 X-100 AC5" },
{ fail,    ""               },
{ fail,    "  "             },
{ succeed, "N1"             },
{ succeed, " N1"            },
{ succeed, "N1 "            },
{ succeed, " N1 "           },
{ fail,    "N 1"            },
{ fail,    "N0"             },
{ succeed, "N9999"          },
{ fail,    "N10000"         },
};
for (auto test : tests) {
std::istringstream input(test.data);
typedef boost::spirit::classic::position_iterator2<boost::spirit::istream_iterator> pos_iterator_type;
pos_iterator_type position_begin(boost::spirit::istream_iterator{input >> std::noskipws}, {}), position_end;
attr_defs sym;
sym.add
("N",  {"N", {1, 9999}})
("X",  {"X", {-999, 999}})
("AC", {"AC", {-99, 999}})
;
all_attributes_grammar<pos_iterator_type> all_attr_gr(sym);
try {
std::vector<AttributeVariant> value;
std::cout << " --------- '" << test.data << "'n";
bool actual = qi::phrase_parse(position_begin, position_end, all_attr_gr, qi::blank, value);
std::cout << ((test.expect == actual)?"PASS":"FAIL");
if (actual) {
std::cout << "t";
for (auto& attr : value)
std::cout << boost::fusion::as_vector(boost::get<AttributeData>(attr)) << " ";
std::cout << "n";
} else {
std::cout << "t(no valid parse)n";
}
}
catch (const qi::expectation_failure<pos_iterator_type>& e) {
auto& pos = e.first.get_position();
std::cout <<
"Parse error at line " << pos.line << " column " << pos.column << ":" << std::endl <<
"'" << e.first.get_currentline() << "'" << std::endl <<
std::setw(pos.column) << " " << "^- here" << std::endl;
}
if (position_begin != position_end)
std::cout << " -> Remaining '" << std::string(position_begin, position_end) << "'n";
}
}

指纹：

--------- 'N100 X-100 AC5'
PASS    (AttrDef(N, 1, 9999) 100) (AttrDef(X, -999, 999) -100) (AttrDef(AC, -99, 999) 5) 
--------- ''
PASS    (no valid parse)
--------- '  '
PASS    (no valid parse)
-> Remaining '  '
--------- 'N1'
PASS    (AttrDef(N, 1, 9999) 1) 
--------- ' N1'
PASS    (AttrDef(N, 1, 9999) 1) 
--------- 'N1 '
PASS    (AttrDef(N, 1, 9999) 1) 
--------- ' N1 '
PASS    (AttrDef(N, 1, 9999) 1) 
--------- 'N 1'
PASS    (no valid parse)
-> Remaining 'N 1'
--------- 'N0'
PASS    (no valid parse)
-> Remaining 'N0'
--------- 'N9999'
PASS    (AttrDef(N, 1, 9999) 9999) 
--------- 'N10000'
PASS    (no valid parse)
-> Remaining 'N10000'

在对提升精神进行了更多研究之后，我发现解决方案是使用局部变量和继承属性：

template <typename Iterator>
class single_attribute_grammar : public qi::grammar<Iterator, AttributeData(), qi::locals<WordGrammar>, qi::blank_type>
{
public:
single_attribute_grammar(const word_symbols &words) : single_attribute_grammar::base_type(single_attribute_rule)
{
auto attr_word = phx::bind(&AttributeData::word, qi::_val);
auto grammar_word = phx::bind(&WordGrammar::word, qi::_1);
auto attr_value = phx::bind(&AttributeData::value, qi::_val);
word_rule = words;
BOOST_SPIRIT_DEBUG_NODE(word_rule);
range_check_rule = qi::eps(phx::bind(verify_range, qi::_r1, qi::_r2));
BOOST_SPIRIT_DEBUG_NODE(range_check_rule);
single_attribute_rule = qi::lexeme[word_rule[attr_word = grammar_word,qi::_a=qi::_1] >
qi::int_[attr_value = qi::_1] > (qi::space|qi::eoi)] >>
range_check_rule(qi::_a, qi::_val);
BOOST_SPIRIT_DEBUG_NODE(single_attribute_rule);
}
private:
qi::rule<Iterator, WordGrammar()> word_rule;
qi::rule<Iterator, void(const WordGrammar&, const AttributeData&), qi::blank_type> range_check_rule;
qi::rule<Iterator, AttributeData(), qi::locals<WordGrammar>, qi::blank_type> single_attribute_rule;
};

还因为我使用BOOST_SPIRIT_DEBUG_NODE流运算符的重载WordGrammar是必要的：

std::ostream& operator<<(std::ostream& ostr, const WordGrammar& grammar)
{
ostr << "WordGrammar(" << grammar.word << ", " << grammar.range_from << ", " << grammar.range_to << ")";
return ostr;
}