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Java > Open Source Codes > org > armedbear > lisp > logbitp


1 /*
2  * logbitp.java
3  *
4  * Copyright (C) 2003-2004 Peter Graves
5  * $Id: logbitp.java,v 1.6 2004/04/24 15:49:22 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 JavaDoc;
25
26 // ### logbitp
27 // logbitp index integer => generalized-boolean
28 public final class logbitp extends Primitive2
29 {
30     private logbitp()
31     {
32         super("logbitp", "index integer");
33     }
34
35     public LispObject execute(LispObject first, LispObject second)
36         throws ConditionThrowable
37     {
38         int index = -1;
39         if (first instanceof Fixnum) {
40             index = ((Fixnum)first).getValue();
41         } else if (first instanceof Bignum) {
42             // FIXME If the number is really big, we're not checking the right
43 // bit...
44 if (((Bignum)first).getValue().signum() > 0)
45                 index = Integer.MAX_VALUE;
46         }
47         if (index < 0)
48             return signal(new TypeError(first, "non-negative integer"));
49         BigInteger JavaDoc n;
50         if (second instanceof Fixnum)
51             n = ((Fixnum)second).getBigInteger();
52         else if (second instanceof Bignum)
53             n = ((Bignum)second).getValue();
54         else
55             return signal(new TypeError(second, Symbol.INTEGER));
56         // FIXME See above.
57 if (index == Integer.MAX_VALUE)
58             return n.signum() < 0 ? T : NIL;
59         return n.testBit(index) ? T : NIL;
60     }
61
62     private static final Primitive2 LOGBITP = new logbitp();
63 }
64
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