/* Variable Java class declaration and implementation.
   Copyright (C) 2001-2010 Roberto Bagnara <bagnara@cs.unipr.it>
   Copyright (C) 2010-2017 BUGSENG srl (http://bugseng.com)

This file is part of the Parma Polyhedra Library (PPL).

The PPL 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 3 of the License, or (at your
option) any later version.

The PPL 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., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1307, USA.

For the most up-to-date information see the Parma Polyhedra Library
site: http://bugseng.com/products/ppl/ . */

package parma_polyhedra_library;

import javax.management.RuntimeErrorException;

//! A dimension of the vector space.
/*! \ingroup PPL_Java_interface
  An object of the class Variable represents a dimension of the space,
  that is one of the Cartesian axes.
  Variables are used as basic blocks in order to build
  more complex linear expressions.
  Each variable is identified by a non-negative integer,
  representing the index of the corresponding Cartesian axis
  (the first axis has index 0).
*/
public class Variable implements Comparable<Variable> {
    //! The index of the Cartesian axis.
    private long varid;

    //! Builds the variable corresponding to the Cartesian axis of index \p i.
    /*!
      \exception RuntimeErrorException
      Thrown if <CODE>i</CODE> is has negative value.
    */
    public Variable(long i) {
        if (i < 0)
            throw new
                RuntimeErrorException(new Error("parma_polyhedra_library.Variable::"
                                                + "Variable:"
                                                + " an index variable"
                                                + " cannot be negative."));
        varid = i;
    }

    //! Returns the index of the Cartesian axis associated to \p this.
    public long id() {
        return varid;
    }

    /*! \brief
      Returns a negative number if \p this is smaller than \p v,
      a zero if \p this equals \p v, a positive number if \p v
      is greater than \p v.
    */
    public int compareTo(Variable v) {
        if (varid < v.varid)
            return -1;
        else if (varid == v.varid)
            return 0;
        else
            return 1;
    }

    //! Optional customization provider for \c toString.
    private static Variable_Stringifier stringifier;

    /*! \brief
      Sets the variable stringifier object.

      A variable stringifier object provides customization for the
      \c toString method; if no variable stringifier object is set
      (or if it is set to a null refeerence value), the PPL default
      variable output function will be used.
    */
    public static native void setStringifier(Variable_Stringifier vs);

    public native String toString();

    private static native void initIDs();
    static {
        initIDs();
    }
}
