logcount


1   /*
2    * logcount.java
3    *
4    * Copyright (C) 2003 Peter Graves
5    * $Id: logcount.java,v 1.3 2003/12/13 00:58:51 piso Exp $
6    *
7    * This program is free software; you can redistribute it and/or
8    * modify it under the terms of the GNU General Public License
9    * as published by the Free Software Foundation; either version 2
10   * of the License, or (at your option) any later version.
11   *
12   * This program is distributed in the hope that it will be useful,
13   * but WITHOUT ANY WARRANTY; without even the implied warranty of
14   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   * GNU General Public License for more details.
16   *
17   * You should have received a copy of the GNU General Public License
18   * along with this program; if not, write to the Free Software
19   * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
20   */
21  
22  package org.armedbear.lisp;
23  
24  import java.math.BigInteger  ;
25  
26  // ### logcount
27  // logcount integer => number-of-on-bits
28  public final class logcount extends Primitive1
29  {
30      private logcount()
31      {
32          super("logcount","integer");
33      }
34  
35      // FIXME Optimize fixnum case!
36      public LispObject execute(LispObject arg) throws ConditionThrowable
37      {
38          BigInteger   n;
39          if (arg instanceof Fixnum)
40              n = ((Fixnum)arg).getBigInteger();
41          else if (arg instanceof Bignum)
42              n = ((Bignum)arg).getValue();
43          else
44              return signal(new TypeError(arg, "integer"));
45          return new Fixnum(n.bitCount());
46      }
47  
48      private static final logcount LOGCOUNT = new logcount();
49  }
50
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