/**
 * @file mix_cc/matheval/ast.hpp
 * @brief 抽象语法树
 * @author Cat (null.null.null@qq.com)
 * @version 0.1
 * @date 2021-09-17
 * 
 * Copyright: Baosight Co. Ltd.
 * DO NOT COPY/USE WITHOUT PERMISSION
 * 
 */
#ifndef MATHEVAL_IMPLEMENTATION
#error "Do not include ast.hpp directly!"
#endif

#pragma once

#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/support/ast/variant.hpp>

#include <list>
#include <string>

namespace mix_cc {

namespace matheval {

namespace x3 = boost::spirit::x3;

namespace ast {

struct nil {};
struct unary_op;
struct binary_op;
struct expression;

// clang-format off
struct operand : x3::variant<
                 nil
                 , double
                 , std::string
                 , x3::forward_ast<unary_op>
                 , x3::forward_ast<binary_op>
                 , x3::forward_ast<expression>
                 > {
    using base_type::base_type;
    using base_type::operator=;
};
// clang-format on

struct unary_op {
  double (*op)(double);
  operand rhs;
};

struct binary_op {
  double (*op)(double, double);
  operand lhs;
  operand rhs;
};

struct operation {
  double (*op)(double, double);
  operand rhs;
};

struct expression {
  operand lhs;
  std::list<operation> rhs;
};

}  // namespace ast

}  // namespace matheval

}  // namespace mix_cc