如何引用符号 table 中的值？
How to refer to value from symbol table?
我不知道如何将符号 table 的值传递给函数。
template <typename Iterator>
class single_attribute_grammar : public qi::grammar<Iterator, AttributeData(), 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);
single_attribute_rule = qi::lexeme[words[attr_word = grammar_word] >
qi::int_[attr_value = qi::_1] > (qi::space|qi::eoi)] >>
qi::eps(phx::bind(verify_range, qi::_r1, qi::_val)); // <-- HERE is the problem
BOOST_SPIRIT_DEBUG_NODE(single_attribute_rule);
}
private:
qi::rule<Iterator, AttributeData(), qi::blank_type> single_attribute_rule;
};
我认为我可以使用 qi::_r1 引用找到的键的值，但代码无法编译：
main.cpp:72:31: required from ‘single_attribute_grammar<Iterator>::single_attribute_grammar(const word_symbols&) [with Iterator = boost::spirit::classic::position_iterator2<boost::spirit::multi_pass<std::istreambuf_iterator<char, std::char_traits<char> > > >; word_symbols = boost::spirit::qi::symbols<char, WordGrammar>]’
main.cpp:87:16: required from ‘all_attributes_grammar<Iterator>::all_attributes_grammar(const word_symbols&) [with Iterator = boost::spirit::classic::position_iterator2<boost::spirit::multi_pass<std::istreambuf_iterator<char, std::char_traits<char> > > >; word_symbols = boost::spirit::qi::symbols<char, WordGrammar>]’
main.cpp:130:62: required from here
/usr/include/boost/spirit/home/support/context.hpp:180:13: error: static assertion failed: index_is_out_of_bounds
BOOST_SPIRIT_ASSERT_MSG(
^
In file included from /usr/include/boost/spirit/home/qi/domain.hpp:18:0,
from /usr/include/boost/spirit/home/qi/meta_compiler.hpp:15,
from /usr/include/boost/spirit/home/qi/action/action.hpp:14,
from /usr/include/boost/spirit/home/qi/action.hpp:14,
from /usr/include/boost/spirit/home/qi.hpp:14,
from /usr/include/boost/spirit/include/qi.hpp:16,
from main.cpp:11:
/usr/include/boost/spirit/home/support/context.hpp:186:13: error: no type named ‘type’ in ‘struct boost::fusion::result_of::at_c<boost::fusion::cons<AttributeData&, boost::fusion::nil_>, 1>’
type;
^~~~
如果此处有帮助，请参阅 MVCE。
#include <iomanip>
#include <string>
#include <vector>
#include <boost/variant.hpp>
#include <boost/optional/optional.hpp>
#define BOOST_SPIRIT_DEBUG
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/qi_symbols.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <boost/spirit/include/phoenix_object.hpp> // construct
#include <boost/spirit/include/support_multi_pass.hpp>
#include <boost/spirit/include/classic_position_iterator.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/phoenix/bind.hpp>
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace classic = boost::spirit::classic;
namespace phx = boost::phoenix;
namespace fusion = boost::fusion;
struct AttributeData
{
std::string word;
int value;
};
using AttributeVariant = boost::variant<
AttributeData
>;
struct WordGrammar
{
std::string word;
int range_from;
int range_to;
};
BOOST_FUSION_ADAPT_STRUCT(
AttributeData,
(std::string, word)
(int, value)
)
using word_symbols = qi::symbols<char, WordGrammar>;
bool verify_range(const WordGrammar &grammar, const AttributeData &data)
{
if(data.value < grammar.range_from || data.value > grammar.range_to)
{
return false;
}
return true;
}
template <typename Iterator>
class single_attribute_grammar : public qi::grammar<Iterator, AttributeData(), 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);
single_attribute_rule = qi::lexeme[words[attr_word = grammar_word] >
qi::int_[attr_value = qi::_1] > (qi::space|qi::eoi)] >>
qi::eps(phx::bind(verify_range, qi::_r1, qi::_val)); // <-- HERE is the problem
BOOST_SPIRIT_DEBUG_NODE(single_attribute_rule);
}
private:
qi::rule<Iterator, AttributeData(), qi::blank_type> single_attribute_rule;
};
template <typename Iterator>
class all_attributes_grammar : public qi::grammar<Iterator, std::vector<AttributeVariant>(), qi::blank_type>
{
public:
all_attributes_grammar(const word_symbols &words) : all_attributes_grammar::base_type(line_attribute_vec_rule)
, sag(words)
{
line_attribute_rule = (
sag
);
BOOST_SPIRIT_DEBUG_NODE(line_attribute_rule);
line_attribute_vec_rule = (line_attribute_rule % *qi::blank) > qi::eoi;
BOOST_SPIRIT_DEBUG_NODE(line_attribute_vec_rule);
}
private:
single_attribute_grammar<Iterator> sag;
qi::rule<Iterator, AttributeVariant(), qi::blank_type> line_attribute_rule;
qi::rule<Iterator, std::vector<AttributeVariant>(), qi::blank_type> line_attribute_vec_rule;
};
int main()
{
std::vector<AttributeVariant> value;
std::string data{"N100 X-100 AC5"};
std::istringstream input(data);
// iterate over stream input
typedef std::istreambuf_iterator<char> base_iterator_type;
base_iterator_type in_begin(input);
// convert input iterator to forward iterator, usable by spirit parser
typedef boost::spirit::multi_pass<base_iterator_type> forward_iterator_type;
forward_iterator_type fwd_begin = boost::spirit::make_default_multi_pass(in_begin);
forward_iterator_type fwd_end;
// wrap forward iterator with position iterator, to record the position
typedef classic::position_iterator2<forward_iterator_type> pos_iterator_type;
pos_iterator_type position_begin(fwd_begin, fwd_end);
pos_iterator_type position_end;
word_symbols 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
{
qi::phrase_parse(position_begin, position_end, all_attr_gr, qi::blank, value);
}
catch (const qi::expectation_failure<pos_iterator_type>& e)
{
const classic::file_position_base<std::string>& 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;
}
return 0;
}
有什么想法吗？
在对 boost spirit 进行更多研究后，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;
};
也因为我使用 BOOST_SPIRIT_DEBUG_NODE 重载流运算符 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;
}
很多事情要简化。
- 当您改为使用语义操作时，为什么要调整 AttributeData？ （参见 Boost Spirit: "Semantic actions are evil"?）
- 使用 skipper 时跳过空格要优雅得多。跳过词素内的空格在逻辑上也是矛盾的（参见Boost spirit skipper issues）
特别是此处跳过空格：
line_attribute_vec_rule = (line_attribute_rule % *qi::blank) > qi::eoi;
完全无效（因为空格已经被跳过，所以 *qi::blank 永远不会匹配任何字符）。整个事情减少到 +line_attribute_rule.
line_attribute_vec_rule = +line_attribute_rule > qi::eoi;
回复：您的回答
确实，您可以在规则中使用更多状态。相反，我会简化 AST 来支持你的情况。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不会在意跳过，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，我完全违背了自己的指导方针 ("avoid semantic actions")，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（具体来说，使用 boost::spirit::istream_iterator 而不是自己进行多通道自适应），我会得出这样的结论：
//#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";
}
}
打印：
--------- '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'
我不知道如何将符号 table 的值传递给函数。
template <typename Iterator>
class single_attribute_grammar : public qi::grammar<Iterator, AttributeData(), 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);
single_attribute_rule = qi::lexeme[words[attr_word = grammar_word] >
qi::int_[attr_value = qi::_1] > (qi::space|qi::eoi)] >>
qi::eps(phx::bind(verify_range, qi::_r1, qi::_val)); // <-- HERE is the problem
BOOST_SPIRIT_DEBUG_NODE(single_attribute_rule);
}
private:
qi::rule<Iterator, AttributeData(), qi::blank_type> single_attribute_rule;
};
我认为我可以使用 qi::_r1 引用找到的键的值，但代码无法编译：
main.cpp:72:31: required from ‘single_attribute_grammar<Iterator>::single_attribute_grammar(const word_symbols&) [with Iterator = boost::spirit::classic::position_iterator2<boost::spirit::multi_pass<std::istreambuf_iterator<char, std::char_traits<char> > > >; word_symbols = boost::spirit::qi::symbols<char, WordGrammar>]’
main.cpp:87:16: required from ‘all_attributes_grammar<Iterator>::all_attributes_grammar(const word_symbols&) [with Iterator = boost::spirit::classic::position_iterator2<boost::spirit::multi_pass<std::istreambuf_iterator<char, std::char_traits<char> > > >; word_symbols = boost::spirit::qi::symbols<char, WordGrammar>]’
main.cpp:130:62: required from here
/usr/include/boost/spirit/home/support/context.hpp:180:13: error: static assertion failed: index_is_out_of_bounds
BOOST_SPIRIT_ASSERT_MSG(
^
In file included from /usr/include/boost/spirit/home/qi/domain.hpp:18:0,
from /usr/include/boost/spirit/home/qi/meta_compiler.hpp:15,
from /usr/include/boost/spirit/home/qi/action/action.hpp:14,
from /usr/include/boost/spirit/home/qi/action.hpp:14,
from /usr/include/boost/spirit/home/qi.hpp:14,
from /usr/include/boost/spirit/include/qi.hpp:16,
from main.cpp:11:
/usr/include/boost/spirit/home/support/context.hpp:186:13: error: no type named ‘type’ in ‘struct boost::fusion::result_of::at_c<boost::fusion::cons<AttributeData&, boost::fusion::nil_>, 1>’
type;
^~~~
如果此处有帮助，请参阅 MVCE。
#include <iomanip>
#include <string>
#include <vector>
#include <boost/variant.hpp>
#include <boost/optional/optional.hpp>
#define BOOST_SPIRIT_DEBUG
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/qi_symbols.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <boost/spirit/include/phoenix_object.hpp> // construct
#include <boost/spirit/include/support_multi_pass.hpp>
#include <boost/spirit/include/classic_position_iterator.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/phoenix/bind.hpp>
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace classic = boost::spirit::classic;
namespace phx = boost::phoenix;
namespace fusion = boost::fusion;
struct AttributeData
{
std::string word;
int value;
};
using AttributeVariant = boost::variant<
AttributeData
>;
struct WordGrammar
{
std::string word;
int range_from;
int range_to;
};
BOOST_FUSION_ADAPT_STRUCT(
AttributeData,
(std::string, word)
(int, value)
)
using word_symbols = qi::symbols<char, WordGrammar>;
bool verify_range(const WordGrammar &grammar, const AttributeData &data)
{
if(data.value < grammar.range_from || data.value > grammar.range_to)
{
return false;
}
return true;
}
template <typename Iterator>
class single_attribute_grammar : public qi::grammar<Iterator, AttributeData(), 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);
single_attribute_rule = qi::lexeme[words[attr_word = grammar_word] >
qi::int_[attr_value = qi::_1] > (qi::space|qi::eoi)] >>
qi::eps(phx::bind(verify_range, qi::_r1, qi::_val)); // <-- HERE is the problem
BOOST_SPIRIT_DEBUG_NODE(single_attribute_rule);
}
private:
qi::rule<Iterator, AttributeData(), qi::blank_type> single_attribute_rule;
};
template <typename Iterator>
class all_attributes_grammar : public qi::grammar<Iterator, std::vector<AttributeVariant>(), qi::blank_type>
{
public:
all_attributes_grammar(const word_symbols &words) : all_attributes_grammar::base_type(line_attribute_vec_rule)
, sag(words)
{
line_attribute_rule = (
sag
);
BOOST_SPIRIT_DEBUG_NODE(line_attribute_rule);
line_attribute_vec_rule = (line_attribute_rule % *qi::blank) > qi::eoi;
BOOST_SPIRIT_DEBUG_NODE(line_attribute_vec_rule);
}
private:
single_attribute_grammar<Iterator> sag;
qi::rule<Iterator, AttributeVariant(), qi::blank_type> line_attribute_rule;
qi::rule<Iterator, std::vector<AttributeVariant>(), qi::blank_type> line_attribute_vec_rule;
};
int main()
{
std::vector<AttributeVariant> value;
std::string data{"N100 X-100 AC5"};
std::istringstream input(data);
// iterate over stream input
typedef std::istreambuf_iterator<char> base_iterator_type;
base_iterator_type in_begin(input);
// convert input iterator to forward iterator, usable by spirit parser
typedef boost::spirit::multi_pass<base_iterator_type> forward_iterator_type;
forward_iterator_type fwd_begin = boost::spirit::make_default_multi_pass(in_begin);
forward_iterator_type fwd_end;
// wrap forward iterator with position iterator, to record the position
typedef classic::position_iterator2<forward_iterator_type> pos_iterator_type;
pos_iterator_type position_begin(fwd_begin, fwd_end);
pos_iterator_type position_end;
word_symbols 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
{
qi::phrase_parse(position_begin, position_end, all_attr_gr, qi::blank, value);
}
catch (const qi::expectation_failure<pos_iterator_type>& e)
{
const classic::file_position_base<std::string>& 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;
}
return 0;
}
有什么想法吗？
在对 boost spirit 进行更多研究后，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;
};
也因为我使用 BOOST_SPIRIT_DEBUG_NODE 重载流运算符 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;
}
很多事情要简化。
- 当您改为使用语义操作时，为什么要调整 AttributeData？ （参见 Boost Spirit: "Semantic actions are evil"?）
- 使用 skipper 时跳过空格要优雅得多。跳过词素内的空格在逻辑上也是矛盾的（参见Boost spirit skipper issues）
特别是此处跳过空格：
line_attribute_vec_rule = (line_attribute_rule % *qi::blank) > qi::eoi;完全无效（因为空格已经被跳过，所以
*qi::blank永远不会匹配任何字符）。整个事情减少到+line_attribute_rule.line_attribute_vec_rule = +line_attribute_rule > qi::eoi;
回复：您的回答
确实，您可以在规则中使用更多状态。相反，我会简化 AST 来支持你的情况。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不会在意跳过，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，我完全违背了自己的指导方针 ("avoid semantic actions")，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（具体来说，使用 boost::spirit::istream_iterator 而不是自己进行多通道自适应），我会得出这样的结论：
//#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";
}
}
打印：
--------- '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'