c – Spirit qi解析为嵌套函数的抽象语法树
作者：互联网
我正在尝试使用boost的精神qi解析器创建一个解析器.它正在解析包含三种类型值的字符串.常量,变量或函数.这些函数可以嵌套在一起.测试串是f(a,b)= f(g(z,x),g(x,h(x)),c),其中a-e是常数,f-r是函数,s-z是变量.我成功创建了一个可以正确解析表达式的规则.当我将解析规则的函数更改为grammar时,出现了麻烦.我可以解决几个错误.我几乎得到语法来解析表达式并将其转换为我创建的抽象语法树.但是我得到了关于boost库中包含的文件的错误,我无法弄清楚它来自哪里因为我不理解编译器消息.我按照网站上的示例,使用员工示例将数据从解析器放到结构中：http://www.boost.org/doc/libs/1_41_0/libs/spirit/example/qi/employee.cpp
main.cpp中
#include "Parser.h"
#include "Term.h"
#include <boost/spirit/include/qi.hpp>
#include <string>
#include <iostream>
#include <list>
using std::string;
using std::cout;
using std::endl;
int main()
{
cout << "Unification Algorithm" << endl << endl;
string phrase = "f(a, b) = f(g(z, x), g(x, h(x)), c)";
string::const_iterator itr = phrase.begin();
string::const_iterator last = phrase.end();
cout << phrase << endl;
// Parser grammar
Parser<string::const_iterator> g;
// Output data
Expression expression;
if (phrase_parse(itr, last, g, boost::spirit::ascii::space, expression))
{
cout << "Expression parsed." << endl;
}
else
{
cout << "Could not parse expression." << endl;
}
}
Parser.h
#ifndef _Parser_h_
#define _Parser_h_
#include "Term.h"
#include <boost/spirit/include/qi.hpp>
#include <vector>
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
template <typename Iterator>
struct Parser : qi::grammar<Iterator, Expression(), ascii::space_type>
{
Parser() : Parser::base_type(expression)
{
using qi::char_;
const_char = char_("a-eA-E");
fn_char = char_("f-rF-R");
var_char = char_("s-zS-Z");
basic_fn = fn_char >> char_('(') >> (const_char | var_char) % char_(',') >> char_(')');
first_fn_wrapper = fn_char >> char_('(') >> (basic_fn | const_char | var_char) % char_(',') >> char_(')');
nested_fn = fn_char >> char_('(') >> (first_fn_wrapper | const_char | var_char) % char_(',') >> char_(')');
expression = nested_fn >> char_("=") >> nested_fn;
}
// Constant character a - e
qi::rule<Iterator, T_Cons, ascii::space_type> const_char;
// Function character f - r
qi::rule<Iterator, char(), ascii::space_type> fn_char;
// Variable character s - z
qi::rule<Iterator, T_Var, ascii::space_type> var_char;
// Allows for basic function parsing eg. f(x, y, z)
qi::rule<Iterator, T_Fn, ascii::space_type> basic_fn;
// Allows for single nested functions eg. f(g(x), y, z)
qi::rule<Iterator, T_Fn, ascii::space_type> first_fn_wrapper;
// Allows for fully nested functions eg. f(g(x, h(y)), z) and so on
qi::rule<Iterator, T_Fn, ascii::space_type> nested_fn;
// Full rule for a nested function expression
qi::rule<Iterator, Expression, ascii::space_type> expression;
};
#endif // _Parser_h_
Term.h
#ifndef _Term_h_
#define _Term_h_
#include <boost/fusion/include/adapt_struct.hpp>
#include <vector>
struct Term
{
char name;
};
BOOST_FUSION_ADAPT_STRUCT(Term, (char, name))
struct T_Cons : Term
{
};
BOOST_FUSION_ADAPT_STRUCT(T_Cons, (char, name))
struct T_Var : Term
{
};
BOOST_FUSION_ADAPT_STRUCT(T_Var, (char, name))
struct T_Fn : Term
{
std::vector<Term> * params;
T_Fn() { params = new std::vector<Term>(); }
~T_Fn() { delete params; }
};
BOOST_FUSION_ADAPT_STRUCT(T_Fn, (std::vector<Term>*, params))
struct Expression
{
Term lh_term;
Term rh_term;
};
BOOST_FUSION_ADAPT_STRUCT(Expression, (char, name) (Term, lh_term) (Term, rh_term))
#endif // _Term_h_
我无法链接编译器的整个错误消息,因为它非常长,但这里是最后几个.这些是它给出的编译错误：
boost_1_46_0\boost\mpl\assert.hpp|360|error: no matching function for call to 'assertion_failed(mpl_::failed************ (boost::spirit::qi::grammar<Iterator, T1, T2, T3, T4>::grammar(const boost::spirit::qi::rule<Iterator_, T1_, T2_, T3_, T4_>&, const string&) [with Iterator_ = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >; T1_ = Expression; T2_ = boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::asci|
boost_1_46_0\boost\proto\extends.hpp|540|error: use of deleted function 'boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, Expression(), boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0l>, boost::spirit::unused_type, boost::spirit::unused_type> > >, 0l>:|
boost_1_46_0\boost\proto\detail\expr0.hpp|165|error: no matching function for call to 'boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, Expression(), boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0l>, boost::spirit::unused_type, boost::spirit::unused_type> >::reference()'|
解决方法:
UPDATE Showing a simplified parser with a a recursive ast parsing the sample expression shown
与往常一样,断言消息导致了问题：
// If you see the assertion below failing then the start rule
// passed to the constructor of the grammar is not compatible with
// the grammar (i.e. it uses different template parameters).
BOOST_SPIRIT_ASSERT_MSG(
(is_same<start_type, rule<Iterator_, T1_, T2_, T3_, T4_> >::value)
, incompatible_start_rule, (rule<Iterator_, T1_, T2_, T3_, T4_>));
所以它告诉你应该将语法与开始规则相匹配：你有
struct Parser : qi::grammar<Iterator, Expression(), ascii::space_type>
但
qi::rule<Iterator, Expression, ascii::space_type> expression;
显然你忘记了括号：
qi::rule<Iterator, Expression(), ascii::space_type> expression;
使用通用库时的准则：
其中一些“规则”通常适用,但没有. 2与Boost Spirit特别相关：
>宝贝步骤;从小开始(空,均匀)
>从AST开始,完全匹配语法
>逐渐建立,
>编制沿途的每一步
UPDATE
这是一个非常简化的语法.如前所述,在之前的“精神第一规则”中,从AST开始,完全匹配语法：
namespace ast {
namespace tag {
struct constant;
struct variable;
struct function;
}
template <typename Tag> struct Identifier { char name; };
using Constant = Identifier<tag::constant>;
using Variable = Identifier<tag::variable>;
using Function = Identifier<tag::function>;
struct FunctionCall;
using Expression = boost::make_recursive_variant<
Constant,
Variable,
boost::recursive_wrapper<FunctionCall>
>::type;
struct FunctionCall {
Function function;
std::vector<Expression> params;
};
struct Equation {
Expression lhs, rhs;
};
}
当然,这可能更简单,因为所有标识符都只是char,你可以动态切换(impression).
现在,语法必须遵循. 1.保持简单2.仔细格式化3.直接匹配ast,4.添加调试宏：
template <typename It, typename Skipper = ascii::space_type>
struct Parser : qi::grammar<It, ast::Equation(), Skipper>
{
Parser() : Parser::base_type(equation_)
{
using namespace qi;
constant_ = qi::eps >> char_("a-eA-E");
function_ = qi::eps >> char_("f-rF-R");
variable_ = qi::eps >> char_("s-zS-Z");
function_call = function_ >> '(' >> -(expression_ % ',') >> ')';
expression_ = constant_ | variable_ | function_call;
equation_ = expression_ >> '=' >> expression_;
BOOST_SPIRIT_DEBUG_NODES((constant_)(function_)(variable_)(function_call)(expression_)(equation_))
}
qi::rule<It, ast::Constant()> constant_;
qi::rule<It, ast::Function()> function_;
qi::rule<It, ast::Variable()> variable_;
qi::rule<It, ast::FunctionCall(), Skipper> function_call;
qi::rule<It, ast::Expression(), Skipper> expression_;
qi::rule<It, ast::Equation(), Skipper> equation_;
};
Note how the comments have become completely unneeded. Also note how recursively using
expression_solved your biggest headache!
完整计划
//#define BOOST_SPIRIT_DEBUG
#include <boost/spirit/include/qi.hpp>
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace ast {
namespace tag {
struct constant;
struct variable;
struct function;
}
template <typename Tag> struct Identifier { char name; };
using Constant = Identifier<tag::constant>;
using Variable = Identifier<tag::variable>;
using Function = Identifier<tag::function>;
struct FunctionCall;
using Expression = boost::make_recursive_variant<
Constant,
Variable,
boost::recursive_wrapper<FunctionCall>
>::type;
struct FunctionCall {
Function function;
std::vector<Expression> params;
};
struct Equation {
Expression lhs, rhs;
};
}
BOOST_FUSION_ADAPT_STRUCT(ast::Constant, (char, name))
BOOST_FUSION_ADAPT_STRUCT(ast::Variable, (char, name))
BOOST_FUSION_ADAPT_STRUCT(ast::Function, (char, name))
BOOST_FUSION_ADAPT_STRUCT(ast::FunctionCall, (ast::Function, function)(std::vector<ast::Expression>, params))
BOOST_FUSION_ADAPT_STRUCT(ast::Equation, (ast::Expression, lhs)(ast::Expression, rhs))
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
template <typename It, typename Skipper = ascii::space_type>
struct Parser : qi::grammar<It, ast::Equation(), Skipper>
{
Parser() : Parser::base_type(equation_)
{
using namespace qi;
constant_ = qi::eps >> char_("a-eA-E");
function_ = qi::eps >> char_("f-rF-R");
variable_ = qi::eps >> char_("s-zS-Z");
function_call = function_ >> '(' >> -(expression_ % ',') >> ')';
expression_ = constant_ | variable_ | function_call;
equation_ = expression_ >> '=' >> expression_;
BOOST_SPIRIT_DEBUG_NODES((constant_)(function_)(variable_)(function_call)(expression_)(equation_))
}
qi::rule<It, ast::Constant()> constant_;
qi::rule<It, ast::Function()> function_;
qi::rule<It, ast::Variable()> variable_;
qi::rule<It, ast::FunctionCall(), Skipper> function_call;
qi::rule<It, ast::Expression(), Skipper> expression_;
qi::rule<It, ast::Equation(), Skipper> equation_;
};
int main() {
std::cout << "Unification Algorithm\n\n";
std::string const phrase = "f(a, b) = f(g(z, x), g(x, h(x)), c)";
using It = std::string::const_iterator;
It itr = phrase.begin(), last = phrase.end();
std::cout << phrase << std::endl;
Parser<It> g;
ast::Equation parsed;
if (phrase_parse(itr, last, g, ascii::space, parsed)) {
std::cout << "Expression parsed.\n";
} else {
std::cout << "Could not parse equation.\n";
}
if (itr != last) {
std::cout << "Remaining unparsed input: '" << std::string(itr,last) << "'\n";
}
}
标签：nested-function,c,parsing,boost,abstract-syntax-tree 来源： https://codeday.me/bug/20190728/1559632.html