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1   ////////////////////////////////////////////////////////////////////////////////
2   // MillScript: an Open Spice interpreter and batch website creation tool
3   // Copyright (C) 2001-2004 Open World Ltd
4   //
5   // This file is part of MillScript.
6   //
7   // MillScript is free software; you can redistribute it and/or modify it under
8   // the terms of the GNU General Public License as published by the Free
9   // Software Foundation; either version 2 of the License, or (at your option)
10  // any later version.
11  //
12  // MillScript is distributed in the hope that it will be useful, but WITHOUT
13  // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14  // FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
15  // more details.
16  //
17  // You should have received a copy of the GNU General Public License along with
18  // MillScript; if not, write to the Free Software Foundation, Inc., 59 Temple
19  // Place, Suite 330, Boston, MA  02111-1307  USA
20  ////////////////////////////////////////////////////////////////////////////////
21  package org.millscript.millscript.action;
22  
23  import org.millscript.millscript.vm.Machine;
24  
25  /**
26   * This class implements the action for a <code>while</code> expression. This
27   * action performs a predicate action and if it's result is <code>true</code> a
28   * body action is performed, otherwise the action ends. Once the body action is
29   * performed we return to the start and perform the predicate again.
30   *
31   * @see org.millscript.millscript.expr.WhileExpr
32   * @see org.millscript.millscript.syntax.WhileSyntax
33   */
34  public final class WhileAction extends Action {
35  
36      /**
37       * The predicate action, which must return a boolean result.
38       */
39      private Action predAct;
40  
41      /**
42       * The body action.
43       */
44      private Action bodyAct;
45  
46      /**
47       * Constructs a new <code>while</code> action, to perform the specified
48       * body action while the specified predicate action returns
49       * <code>true</code>.
50       *
51       * @param a the predicate action
52       * @param b the body action
53       */
54      public WhileAction( final Action a, final Action b ) {
55          this.predAct = a;
56          this.bodyAct = b;
57      }
58  
59      /**
60       * @see org.millscript.millscript.action.Action#action(org.millscript.millscript.vm.Machine)
61       */
62      @Override
63      public void action( final Machine mc ) {
64          while ( predAct.predAct( mc ) ) {
65              bodyAct.act( mc );
66          }
67      }
68  }