/** @file symbol.h
 *
 *  Interface to GiNaC's symbolic objects. */

/*
 *  GiNaC Copyright (C) 1999-2000 Johannes Gutenberg University Mainz, Germany
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef __GINAC_SYMBOL_H__
#define __GINAC_SYMBOL_H__

#include <string>
#include <ginac/basic.h>
#include <ginac/ex.h>

#ifndef NO_GINAC_NAMESPACE
namespace GiNaC {
#endif // ndef NO_GINAC_NAMESPACE

/** Basic CAS symbol.  It has a name because it must know how to output itself.
 *  It may be assigned an expression, but this feature is only intended for
 *  programs like 'ginsh' that want to associate symbols with expressions.
 *  If you want to replace symbols by expressions in your code, you should
 *  use ex::subs() or use objects of class ex instead of class symbol in the
 *  first place. */
class symbol : public basic
{
    GINAC_DECLARE_REGISTERED_CLASS(symbol, basic)

// types

    /** Symbols as keys to expressions. */
    class assigned_ex_info {
    public:
        assigned_ex_info();     //!< Default ctor
        bool is_assigned;       //!< True if there is an expression assigned
        ex assigned_expression; //!< The actual expression
        unsigned refcount;      //!< Yet another refcounter. PLEASE EXPLAIN!
    };
    
// member functions

    // default constructor, destructor, copy constructor assignment operator and helpers
public:
    symbol();
    ~symbol();
    symbol(symbol const & other);
protected:
    void copy(symbol const & other); 
    void destroy(bool call_parent);

    // other constructors
public:
    explicit symbol(string const & initname);

    // functions overriding virtual functions from base classes
public:
    basic * duplicate() const;
    void print(ostream & os, unsigned upper_precedence=0) const;
    void printraw(ostream & os) const;
    void printtree(ostream & os, unsigned indent) const;
    void printcsrc(ostream & os, unsigned type, unsigned upper_precedence=0) const;
    bool info(unsigned inf) const;
    ex expand(unsigned options=0) const;
    bool has(ex const & other) const;
    int degree(symbol const & s) const;
    int ldegree(symbol const & s) const;
    ex coeff(symbol const & s, int const n = 1) const;
    ex eval(int level = 0) const;
    ex diff(symbol const & s) const;
    ex series(symbol const & s, ex const & point, int order) const;
    ex normal(lst &sym_lst, lst &repl_lst, int level=0) const;
    ex subs(lst const & ls, lst const & lr) const;
protected:
    int compare_same_type(basic const & other) const;
    bool is_equal_same_type(basic const & other) const;
    unsigned return_type(void) const;
    unsigned return_type_tinfo(void) const;
    unsigned calchash(void) const;
    
    // non-virtual functions in this class
public:
    void assign(ex const & value);
    void unassign(void);
    ex diff(symbol const & s, unsigned nth) const;
    void setname(string const & n) {name=n;}
    string getname(void) const {return name;}
private:
    string & autoname_prefix(void);

// member variables

protected:
    assigned_ex_info * asexinfop;
    unsigned serial;  //!< unique serial number for comparision
    string name;
private:
    static unsigned next_serial;
};

// global constants

extern const symbol some_symbol;
extern type_info const & typeid_symbol;

// utility functions
inline const symbol &ex_to_symbol(const ex &e)
{
	return static_cast<const symbol &>(*e.bp);
}

// wrapper functions around member functions
inline void unassign(symbol & symarg)
{ return symarg.unassign(); }

inline int degree(symbol const & a, symbol const & s)
{ return a.degree(s); }

inline int ldegree(symbol const & a, symbol const & s)
{ return a.ldegree(s); }

#ifndef NO_GINAC_NAMESPACE
} // namespace GiNaC
#endif // ndef NO_GINAC_NAMESPACE

#endif // ndef __GINAC_SYMBOL_H__