spirit/example/x3/calc/calc4c/grammar.hpp

193 lines
5.4 KiB
C++

/*=============================================================================
Copyright (c) 2001-2014 Joel de Guzman
Copyright (c) 2013-2014 Agustin Berge
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 Calculator example demonstrating generation of AST. The AST,
// once created, is traversed, 1) To print its contents and
// 2) To evaluate the result.
//
// [ JDG April 28, 2008 ] For BoostCon 2008
// [ JDG February 18, 2011 ] Pure attributes. No semantic actions.
// [ JDG January 9, 2013 ] Spirit X3
//
///////////////////////////////////////////////////////////////////////////////
#if defined(_MSC_VER)
# pragma warning(disable: 4345)
#endif
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/variant/recursive_variant.hpp>
#include <boost/variant/apply_visitor.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <list>
#include <numeric>
namespace x3 = boost::spirit::x3;
namespace client { namespace ast
{
///////////////////////////////////////////////////////////////////////////
// The AST
///////////////////////////////////////////////////////////////////////////
struct nil {};
struct signed_;
struct program;
typedef x3::variant<
nil
, unsigned int
, x3::forward_ast<signed_>
, x3::forward_ast<program>
>
operand;
struct signed_
{
char sign;
operand operand_;
};
struct operation
{
char operator_;
operand operand_;
};
struct program
{
operand first;
std::list<operation> rest;
};
}}
BOOST_FUSION_ADAPT_STRUCT(client::ast::signed_,
sign, operand_
)
BOOST_FUSION_ADAPT_STRUCT(client::ast::operation,
operator_, operand_
)
BOOST_FUSION_ADAPT_STRUCT(client::ast::program,
first, rest
)
namespace client { namespace ast
{
///////////////////////////////////////////////////////////////////////////
// The AST Printer
///////////////////////////////////////////////////////////////////////////
struct printer
{
typedef void result_type;
void operator()(nil) const {}
void operator()(unsigned int n) const { std::cout << n; }
void operator()(operation const& x) const
{
boost::apply_visitor(*this, x.operand_);
switch (x.operator_)
{
case '+': std::cout << " add"; break;
case '-': std::cout << " subt"; break;
case '*': std::cout << " mult"; break;
case '/': std::cout << " div"; break;
}
}
void operator()(signed_ const& x) const
{
boost::apply_visitor(*this, x.operand_);
switch (x.sign)
{
case '-': std::cout << " neg"; break;
case '+': std::cout << " pos"; break;
}
}
void operator()(program const& x) const
{
boost::apply_visitor(*this, x.first);
for (operation const& oper: x.rest)
{
std::cout << ' ';
(*this)(oper);
}
}
};
///////////////////////////////////////////////////////////////////////////
// The AST evaluator
///////////////////////////////////////////////////////////////////////////
struct eval
{
typedef int result_type;
int operator()(nil) const { BOOST_ASSERT(0); return 0; }
int operator()(unsigned int n) const { return n; }
int operator()(int lhs, operation const& x) const
{
int rhs = boost::apply_visitor(*this, x.operand_);
switch (x.operator_)
{
case '+': return lhs + rhs;
case '-': return lhs - rhs;
case '*': return lhs * rhs;
case '/': return lhs / rhs;
}
BOOST_ASSERT(0);
return 0;
}
int operator()(signed_ const& x) const
{
int rhs = boost::apply_visitor(*this, x.operand_);
switch (x.sign)
{
case '-': return -rhs;
case '+': return +rhs;
}
BOOST_ASSERT(0);
return 0;
}
int operator()(program const& x) const
{
return std::accumulate( x.rest.begin(), x.rest.end()
, boost::apply_visitor(*this, x.first)
, *this);
}
};
}}
namespace client
{
///////////////////////////////////////////////////////////////////////////////
// The calculator grammar
///////////////////////////////////////////////////////////////////////////////
namespace calculator_grammar
{
using parser_type =
x3::any_parser<
std::string::const_iterator
, ast::program
, decltype(x3::make_context<x3::skipper_tag>(x3::ascii::space))
>;
parser_type calculator();
}
auto const calculator = calculator_grammar::calculator();
}