c – 提升精神报告语义错误
作者：互联网
我正在使用boost.spirit库,我无法通过语义操作报告一个简单的错误消息.
// supported parameter types (int or quoted strings)
parameter = bsqi::int_ | bsqi::lexeme[L'"' > *(bsqi_coding::char_ - L'"') > L'"'];
parameter.name("parameter");
// comma separator list of parameters (or no parameters)
parameters = -(parameter % L',');
parameters.name("parameters");
// action with parameters
action = (Actions > L'(' > parameters > L')')[bsqi::_pass = boost::phoenix::bind(&ValidateAction, bsqi::_1, bsqi::_2)];
action.name("action");
Actions只是一个符号表(boost :: spirit :: qi :: symbols).参数的属性是boost :: variant的std :: vector,它描述了参数类型.我想在语义动作ValidateAction中产生一个有意义的错误消息,同时也指示输入内的位置有什么不对.如果我只是将_pass分配给false,则解析结束但错误消息类似于“期待”,而不是第二个参数有错误的类型(预期int而不是字符串).
在某处我读到我可以从我的语义操作中抛出异常,但问题是我没有找到是否以及如何从解析的值访问迭代器.例如,我想使用expectation_failure异常,因此我的错误处理程序会被自动调用,但我需要将迭代器传递给异常,这似乎是不可能的.
有没有什么好的方法如何报告语义故障与更详细的信息,除了只返回false？
解决方法:
我使用filepos_iterator并抛出异常,因此您可以完全控制报告.
让我看看在剩下的15分钟内我能想出什么
好的,花了一点时间,但认为这是一个有益的演示：
#include <boost/fusion/adapted.hpp>
#include <boost/fusion/include/io.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/spirit/include/support_line_pos_iterator.hpp>
#include <boost/spirit/repository/include/qi_iter_pos.hpp>
#include <boost/lexical_cast.hpp>
namespace qi = boost::spirit::qi;
namespace qr = boost::spirit::repository::qi;
namespace px = boost::phoenix;
namespace qi_coding = boost::spirit::ascii;
using It = boost::spirit::line_pos_iterator<std::string::const_iterator>;
namespace ast {
enum actionid { f_unary, f_binary };
enum param_type { int_param, string_param };
static inline std::ostream& operator<<(std::ostream& os, actionid id) {
switch(id) {
case f_unary: return os << "f_unary";
case f_binary: return os << "f_binary";
default: return os << "(unknown)";
} }
static inline std::ostream& operator<<(std::ostream& os, param_type t) {
switch(t) {
case int_param: return os << "integer";
case string_param: return os << "string";
default: return os << "(unknown)";
} }
using param_value = boost::variant<int, std::string>;
struct parameter {
It position;
param_value value;
friend std::ostream& operator<<(std::ostream& os, parameter const& p) { return os << p.value; }
};
using parameters = std::vector<parameter>;
struct action {
/*
*action() = default;
*template <typename Sequence> action(Sequence const& seq) { boost::fusion::copy(seq, *this); }
*/
actionid id;
parameters params;
};
}
namespace std {
static inline std::ostream& operator<<(std::ostream& os, ast::parameters const& v) {
std::copy(v.begin(), v.end(), std::ostream_iterator<ast::parameter>(os, " "));
return os;
}
}
BOOST_FUSION_ADAPT_STRUCT(ast::action, id, params)
BOOST_FUSION_ADAPT_STRUCT(ast::parameter, position, value)
struct BadAction : std::exception {
It _where;
std::string _what;
BadAction(It it, std::string msg) : _where(it), _what(std::move(msg)) {}
It where() const { return _where; }
char const* what() const noexcept { return _what.c_str(); }
};
struct ValidateAction {
std::map<ast::actionid, std::vector<ast::param_type> > const specs {
{ ast::f_unary, { ast::int_param } },
{ ast::f_binary, { ast::int_param, ast::string_param } },
};
ast::action operator()(It source, ast::action parsed) const {
auto check = [](ast::parameter const& p, ast::param_type expected_type) {
if (p.value.which() != expected_type) {
auto name = boost::lexical_cast<std::string>(expected_type);
throw BadAction(p.position, "Type mismatch (expecting " + name + ")");
}
};
int i;
try {
auto& formals = specs.at(parsed.id);
auto& actuals = parsed.params;
auto arity = formals.size();
for (i=0; i<arity; ++i)
check(actuals.at(i), formals.at(i));
if (actuals.size() > arity)
throw BadAction(actuals.at(arity).position, "Excess parameters");
} catch(std::out_of_range const&) {
throw BadAction(source, "Missing parameter #" + std::to_string(i+1));
}
return parsed;
}
};
template <typename It, typename Skipper = qi::space_type>
struct Parser : qi::grammar<It, ast::action(), Skipper> {
Parser() : Parser::base_type(start) {
using namespace qi;
parameter = qr::iter_pos >> (int_ | lexeme['"' >> *~qi_coding::char_('"') >> '"']);
parameters = -(parameter % ',');
action = actions_ >> '(' >> parameters >> ')';
start = (qr::iter_pos >> action) [ _val = validate_(_1, _2) ];
BOOST_SPIRIT_DEBUG_NODES((parameter)(parameters)(action))
}
private:
qi::rule<It, ast::action(), Skipper> start, action;
qi::rule<It, ast::parameters(), Skipper> parameters;
qi::rule<It, ast::parameter(), Skipper> parameter;
px::function<ValidateAction> validate_;
struct Actions : qi::symbols<char, ast::actionid> {
Actions() { this->add("f_unary", ast::f_unary)("f_binary", ast::f_binary); }
} actions_;
};
int main() {
for (std::string const input : {
// good
"f_unary( 0 )",
"f_binary ( 47, \"hello\")",
// errors
"f_binary ( 47, \"hello\") bogus",
"f_unary ( 47, \"hello\") ",
"f_binary ( 47, \r\n 7) ",
})
{
std::cout << "-----------------------\n";
Parser<It> p;
It f(input.begin()), l(input.end());
auto printErrorContext = [f,l](std::ostream& os, It where) {
auto line = get_current_line(f, where, l);
os << " line:" << get_line(where)
<< ", col:" << get_column(line.begin(), where) << "\n";
while (!line.empty() && std::strchr("\r\n", *line.begin()))
line.advance_begin(1);
std::cerr << line << "\n";
std::cerr << std::string(std::distance(line.begin(), where), ' ') << "^ --- here\n";
};
ast::action data;
try {
if (qi::phrase_parse(f, l, p > qi::eoi, qi::space, data)) {
std::cout << "Parsed: " << boost::fusion::as_vector(data) << "\n";
}
} catch(qi::expectation_failure<It> const& e) {
printErrorContext(std::cerr << "Expectation failed: " << e.what_, e.first);
} catch(BadAction const& ba) {
printErrorContext(std::cerr << "BadAction: " << ba.what(), ba.where());
}
if (f!=l) {
std::cout << "Remaining unparsed: '" << std::string(f,l) << "'\n";
}
}
}
印刷：
-----------------------
Parsed: (f_unary 0 )
-----------------------
Parsed: (f_binary 47 hello )
-----------------------
Expectation failed: <eoi> line:1, col:25
f_binary ( 47, "hello") bogus
^ --- here
Remaining unparsed: 'f_binary ( 47, "hello") bogus'
-----------------------
BadAction: Excess parameters line:1, col:15
f_unary ( 47, "hello")
^ --- here
Remaining unparsed: 'f_unary ( 47, "hello") '
-----------------------
BadAction: Type mismatch (expecting string) line:2, col:8
7)
^ --- here
Remaining unparsed: 'f_binary ( 47,
7) '
标签：boost-spirit-qi,c 来源： https://codeday.me/bug/20191009/1875931.html