cell.hpp

parser in C++~~~~~~~~~~~~

/**
 * \mainpage COMP151 Programming Assignment 1, Spring 2007
 *
 * \author Fok On Man
 * \author 06035253
 * \author cs_fom
 * \author LA2A
 *
 * \date 8 March, 2007
 *
 * Instructor: <a href="http://www.cs.ust.hk/~dekai/">Dekai Wu</a>
 * Due: 2007.03.06 at 23:00 by CASS
 */

/**
 * \file Cell.hpp
 *
 * Encapsulates the abstract interface for a concrete class-based
 * implementation of cells for a cons list data structure.
 */

#ifndef CELL_HPP
#define CELL_HPP

#include <cstddef>
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <stack>

using namespace std;

/**
 * \class Cell
 * \brief Class Cell
 */
class Cell {
public:

  /**
   * \brief Check if this is an int cell.
   * \return True iff this is an int cell.
   */
  bool is_int() const;

  /**
   * \brief Check if this is a double cell.
   * \return True iff this is a double cell.
   */
  bool is_double() const;

  /**
   * \brief Check if this is a symbol cell.
   * \return True iff this is a symbol cell.
   */
  bool is_symbol() const;

  /**
   * \brief Check if this is a cons cell.
   * \return True iff this is a cons cell.
   */
  bool is_cons() const;

  /**
   * \brief Accessor (error if this is not an int cell).
   * \return The value in this int cell.
   */
  int get_int() const;

  /**
   * \brief Accessor (error if this is not a double cell).
   * \return The value in this double cell.
   */
  double get_double() const;

  /**
   * \brief Accessor (error if this is not a symbol cell).
   * \return The symbol name in this symbol cell.
   */
  string get_symbol() const;

  /**
   * \brief Accessor (error if this is not a cons cell).
   * \return First child cell.
   */
  Cell* get_car() const;

  /**
   * \brief Accessor (error if this is not a cons cell).
   * \return Rest child cell.
   */
  Cell* get_cdr() const;

  /**
   * \brief Print the subtree rooted at this cell, in s-expression notation.
   * \param os The output stream to print to.
   */
  void print(ostream& os = cout) const;

private:

  enum TypeTag {type_int, type_double, type_symbol, type_conspair};
  TypeTag tag_m;
  struct ConsPair
  {
    Cell *car;	//!< car this is car pointer
    Cell *cdr;	//!< cdr this is cdr poin
  };
  union
  {
    int int_m;	//!< int_m this is integer cell vaule
    double double_m;	//!< double_m this is double cell vaule
    char* symbol_m;	//!< symbol_m this is symbol cell vaule
    ConsPair conspair_m;	//!< conspair_m this is conspair cell vaule
  };
};

// Reminder: cons.hpp expects nil to be defined somewhere (for this
// implementation, Cell.cpp is the logical place to define it).
// Here we promise this again, just to be safe.
extern Cell* const nil;

#endif // CELL_HPP