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.commons.alert.Alert;
25 import org.millscript.millscript.alert.Alerts;
26 import org.millscript.millscript.vm.Machine;
27
28 /**
29 * This class represents a checked action, which must return no results.
30 */
31 public final class CheckNoneAction extends Action {
32
33 /**
34 * The action to check.
35 */
36 private Action cont;
37
38 /**
39 * Constructs a new check action, which will check to see if the specified
40 * action returns no results.
41 *
42 * @param c the action to check
43 */
44 public CheckNoneAction( final Action c ) {
45 this.cont = c;
46 }
47
48 /**
49 * @see org.millscript.millscript.action.Action#action(org.millscript.millscript.vm.Machine)
50 */
51 @Override
52 public void action( final Machine mc ) {
53 // Store the current number of values on the stack
54 int n = mc.getCount();
55 // Perform the checked action
56 cont.act( mc );
57 // Check that no results were pushed onto the stack by the checked
58 // action
59 if ( mc.getCount() == n ) {
60 return;
61 }
62 // Construct a new alert to report too many results...
63 final Alert alert = Alerts.eval(
64 "Too many results returned while executing statement",
65 "Only the final expression in a statement may return results"
66 );
67 n = mc.getCount() - n;
68 for ( int i = n - 1; i >= 0; i-- ) {
69 alert.culprit( "arg(" + n + ")", mc.popObject() );
70 }
71 // Throw...
72 throw( alert.mishap() );
73 }
74
75 }