content: /*
   *    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., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  
  /*
   *    ExponentialFormat.java
   *    Copyright (C) 2002 University of Waikato, Hamilton, New Zealand
   *
   */
  
  package weka.core.matrix;
  
  import weka.core.RevisionHandler;
  import weka.core.RevisionUtils;
  
  import java.text.DecimalFormat;
  import java.text.FieldPosition;
  
  /**
   * @author Yong Wang
   * @version $Revision: 5953 $
   */
  public class ExponentialFormat
    extends DecimalFormat
    implements RevisionHandler {
  
    /** for serialization */
    private static final long serialVersionUID = -5298981701073897741L;
      
    protected DecimalFormat nf ;
    protected boolean sign;
    protected int digits;
    protected int exp;
    protected boolean trailing = true;
  
    public ExponentialFormat () {
      this( 5 );
    }
      
    public ExponentialFormat( int digits ) {
      this( digits, false );
    }
  
    public ExponentialFormat( int digits, boolean trailing ) {
      this( digits, 2, true, trailing );
    }
      
    public ExponentialFormat( int digits, int exp, boolean sign, 
  			    boolean trailing ) {
      this.digits = digits;
      this.exp = exp;
      this.sign = sign;
      this.trailing = trailing;
      nf = new DecimalFormat( pattern() );
      nf.setPositivePrefix("+");
      nf.setNegativePrefix("-");
    }
      
    public int width () {
      if( !trailing ) throw new RuntimeException( "flexible width" );
      if( sign ) return 1 + digits + 2 + exp;
      else return digits + 2 + exp;
    }
  
    public StringBuffer format(double number, StringBuffer toAppendTo, 
  			     FieldPosition pos) {
      StringBuffer s = new StringBuffer( nf.format(number) );
      if( sign ) {
        if( s.charAt(0) == '+' ) s.setCharAt(0, ' ');
      }
      else {
        if( s.charAt(0) == '-' ) s.setCharAt(0, '*');
        else s.deleteCharAt(0);
      }
  	
      return toAppendTo.append( s );
    }
      
    private String  pattern() {
      StringBuffer s = new StringBuffer();      // "-##0.00E-00"   // fw.d
      s.append("0.");
      for(int i = 0; i < digits - 1; i ++)
        if( trailing ) s.append('0');
        else s.append('#');
  	
      s.append('E');
      for(int i = 0; i < exp; i ++)
        s.append('0');
  	
      return s.toString();
    }
    
    /**
     * Returns the revision string.
     * 
     * @return		the revision
     */
    public String getRevision() {
      return RevisionUtils.extract("$Revision: 5953 $");
    }
  }
  