Change my codes from QI to X3, and get some compile error with BOOST_FUSION_ADAPT_ADT. I tried boost 1.64 and 1.67, neither of them work. I modified the spirit X3 example rexpr_min, adding getter and setter to struct rexpr, changing the BOOST_FUSION_ADAPT_STRUCT to BOOST_FUSION_ADAPT_ADT, and compile it fail, too.
Enviroment:
ubuntu 16.04
G++ 5.4, with
-std=c++17flagboost 1.67
Error message:
boost/spirit/home/x3/core/detail/parse_into_container.hpp:142:35: error: invalid initialization of non-const reference of type ‘boost::fusion::extension::adt_attribute_proxy<client::ast::rexpr, 0, false>&’ from an rvalue of type ‘boost::fusion::extension::deref_impl<boost::fusion::struct_iterator_tag>::apply<boost::fusion::basic_iterator<boost::fusion::struct_iterator_tag, boost::fusion::random_access_traversal_tag, client::ast::rexpr, 0> >::type {aka boost::fusion::extension::adt_attribute_proxy<client::ast::rexpr, 0, false>}’
return call_synthesize(parser, first, last, context, rcontext,
I guess the fusion::front(attr) return a const reference, and the call_synthesize want a non-const reference (at boost_1_64_0/boost/spirit/home/x3/core/detail/parse_into_container.hpp, line 146). But I don't know what to do.
I googled and find some regression of QI and they are patched in newest version. But there is no information with X3.
The original code spirit X3 example rexpr_min, And my modification:
/*=============================================================================
Copyright (c) 2001-2015 Joel de Guzman
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
///////////////////////////////////////////////////////////////////////////////
//
// A simple parser for X3 intended as a minimal starting point.
// 'rexpr' is a parser for a language resembling a minimal subset
// of json, but limited to a dictionary (composed of key=value pairs)
// where the value can itself be a string or a recursive dictionary.
//
// Example:
//
// {
// "color" = "blue"
// "size" = "29 cm."
// "position" = {
// "x" = "123"
// "y" = "456"
// }
// }
//
///////////////////////////////////////////////////////////////////////////////
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/fusion/include/adapt_adt.hpp>
#include <boost/fusion/include/std_pair.hpp>
#include <boost/fusion/include/io.hpp>
#include <iostream>
#include <fstream>
#include <string>
#include <map>
///////////////////////////////////////////////////////////////////////////////
// Our AST
///////////////////////////////////////////////////////////////////////////////
namespace client { namespace ast
{
namespace fusion = boost::fusion;
namespace x3 = boost::spirit::x3;
struct rexpr;
struct rexpr_value : x3::variant<
std::string
, x3::forward_ast<rexpr>
>
{
using base_type::base_type;
using base_type::operator=;
};
typedef std::map<std::string, rexpr_value> rexpr_map;
typedef std::pair<std::string, rexpr_value> rexpr_key_value;
struct rexpr
{
rexpr_map i_entries;
const rexpr_map& entries() const { return i_entries; }
void entries(const rexpr_map& ent) { i_entries = ent; }
};
}}
// We need to tell fusion about our rexpr struct
// to make it a first-class fusion citizen
BOOST_FUSION_ADAPT_ADT(client::ast::rexpr,
(obj.entries(), obj.entries(val))
)
///////////////////////////////////////////////////////////////////////////////
// AST processing
///////////////////////////////////////////////////////////////////////////////
namespace client { namespace ast
{
///////////////////////////////////////////////////////////////////////////
// Print out the rexpr tree
///////////////////////////////////////////////////////////////////////////
int const tabsize = 4;
struct rexpr_printer
{
typedef void result_type;
rexpr_printer(int indent = 0)
: indent(indent) {}
void operator()(rexpr const& ast) const
{
std::cout << '{' << std::endl;
for (auto const& entry : ast.entries())
{
tab(indent+tabsize);
std::cout << '"' << entry.first << "\" = ";
boost::apply_visitor(rexpr_printer(indent+tabsize), entry.second);
}
tab(indent);
std::cout << '}' << std::endl;
}
void operator()(std::string const& text) const
{
std::cout << '"' << text << '"' << std::endl;
}
void tab(int spaces) const
{
for (int i = 0; i < spaces; ++i)
std::cout << ' ';
}
int indent;
};
}}
///////////////////////////////////////////////////////////////////////////////
// Our rexpr grammar
///////////////////////////////////////////////////////////////////////////////
namespace client { namespace parser
{
namespace x3 = boost::spirit::x3;
namespace ascii = boost::spirit::x3::ascii;
using x3::lit;
using x3::lexeme;
using ascii::char_;
using ascii::string;
x3::rule<class rexpr_value, ast::rexpr_value>
rexpr_value = "rexpr_value";
x3::rule<class rexpr, ast::rexpr>
rexpr = "rexpr";
x3::rule<class rexpr_key_value, ast::rexpr_key_value>
rexpr_key_value = "rexpr_key_value";
auto const quoted_string =
lexeme['"' >> *(char_ - '"') >> '"'];
auto const rexpr_value_def =
quoted_string | rexpr;
auto const rexpr_key_value_def =
quoted_string >> '=' >> rexpr_value;
auto const rexpr_def =
'{' >> *rexpr_key_value >> '}';
BOOST_SPIRIT_DEFINE(rexpr_value, rexpr, rexpr_key_value);
}}
///////////////////////////////////////////////////////////////////////////////
// Main program
///////////////////////////////////////////////////////////////////////////////
int main(int argc, char **argv)
{
char const* filename;
if (argc > 1)
{
filename = argv[1];
}
else
{
std::cerr << "Error: No input file provided." << std::endl;
return 1;
}
std::ifstream in(filename, std::ios_base::in);
if (!in)
{
std::cerr << "Error: Could not open input file: "
<< filename << std::endl;
return 1;
}
std::string storage; // We will read the contents here.
in.unsetf(std::ios::skipws); // No white space skipping!
std::copy(
std::istream_iterator<char>(in),
std::istream_iterator<char>(),
std::back_inserter(storage));
using client::parser::rexpr; // Our grammar
client::ast::rexpr ast; // Our tree
using boost::spirit::x3::ascii::space;
std::string::const_iterator iter = storage.begin();
std::string::const_iterator end = storage.end();
bool r = phrase_parse(iter, end, rexpr, space, ast);
if (r && iter == end)
{
std::cout << "-------------------------\n";
std::cout << "Parsing succeeded\n";
std::cout << "-------------------------\n";
client::ast::rexpr_printer printer;
printer(ast);
return 0;
}
else
{
std::string::const_iterator some = iter+30;
std::string context(iter, (some>end)?end:some);
std::cout << "-------------------------\n";
std::cout << "Parsing failed\n";
std::cout << "stopped at: \": " << context << "...\"\n";
std::cout << "-------------------------\n";
return 1;
}
}
for (auto const& entry : ast.entries()). Fix, then x3 complains that the adapted container does not have a value_type. Using ms141 – Gimlet