1 ////////////////////////////////////////////////////////////////////////////////
2 // MillScript: an Open Spice interpreter and batch website creation tool
3 // Copyright (C) 2001-2004 Open World Ltd
4 // Copyright (C) 2005 Kevin Rogers
5 //
6 // This file is part of MillScript.
7 //
8 // MillScript is free software; you can redistribute it and/or modify it under
9 // the terms of the GNU General Public License as published by the Free
10 // Software Foundation; either version 2 of the License, or (at your option)
11 // any later version.
12 //
13 // MillScript is distributed in the hope that it will be useful, but WITHOUT
14 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
16 // more details.
17 //
18 // You should have received a copy of the GNU General Public License along with
19 // MillScript; if not, write to the Free Software Foundation, Inc., 59 Temple
20 // Place, Suite 330, Boston, MA 02111-1307 USA
21 ////////////////////////////////////////////////////////////////////////////////
22 package org.millscript.millscript.action;
23
24 import org.millscript.millscript.alert.Alerts;
25 import org.millscript.millscript.vm.Machine;
26
27 /**
28 * This class represents a checked action, which must return a single result.
29 */
30 public final class CheckAction extends Action {
31
32 /**
33 * The action to check.
34 */
35 private Action cont;
36
37 /**
38 * Constructs a new check action, which will check to see if the specified
39 * action returns one result.
40 *
41 * @param c the action to check
42 */
43 public CheckAction( final Action c ) {
44 cont = c;
45 }
46
47 /**
48 * @see org.millscript.millscript.action.Action#action(org.millscript.millscript.vm.Machine)
49 */
50 @Override
51 public void action( final Machine mc ) {
52 // Store the current number of values on the stack
53 int n = mc.getCount();
54 // Perform the checked action
55 cont.act( mc );
56 // Check that only one result was pushed onto the stack by the checked
57 // action
58 if ( mc.getCount() - n == 1 ) {
59 return;
60 }
61 throw(
62 Alerts.eval(
63 "Wrong number of arguments returned by expression",
64 "Exactly one result required"
65 ).mishap()
66 );
67 }
68
69 }