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


1 /*
2  * assq.java
3  *
4  * Copyright (C) 2003 Peter Graves
5  * $Id: assq.java,v 1.2 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 // ### assq item alist => entry
25
public final class assq extends Primitive2
26 {
27     private assq()
28     {
29         super("assq", PACKAGE_EXT);
30     }
31
32     public LispObject execute(LispObject item, LispObject alist)
33         throws ConditionThrowable
34     {
35         while (alist != NIL) {
36             LispObject cons = alist.car();
37             if (cons instanceof Cons) {
38                 if (cons.car() == item)
39                     return cons;
40             } else if (cons != NIL)
41                 return signal(new TypeError(cons, "list"));
42             alist = alist.cdr();
43         }
44         return NIL;
45     }
46
47     private static final assq ASSQ = new assq();
48 }
49
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