View Javadoc

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.expr;
22  
23  import org.millscript.millscript.action.WhileAction;
24  import org.millscript.millscript.vm.CompilerState;
25  
26  /**
27   * This class implement the <code>while</code> loop syntax. The loop body
28   * expression will be evaluated repeatedly until the predicate expression
29   * evaluates to <code>false</code>.
30   *
31   * @see org.millscript.millscript.syntax.WhileSyntax
32   * @see WhileAction
33   */
34  public final class WhileExpr extends Expr< WhileAction > {
35  
36      /**
37       * The predicate expression.
38       */
39      private final Expr< ? > predExpr;
40  
41      /**
42       * The body expression.
43       */
44      private final Expr< ? > bodyExpr;
45  
46      /**
47       * Creates a new while expression, with the specified predicate and body
48       * expressions.
49       *
50       * @param   a   the predicate expression, should return
51       *              <code>true</code>/<code>false</code>
52       * @param   b   the body expression
53       */
54      public WhileExpr( final Expr< ? > a, final Expr< ? > b ) {
55          predExpr = CheckExpr.make( a );
56          bodyExpr = b;
57      }
58  
59      /**
60       * @see org.millscript.millscript.expr.Expr#compileIt()
61       */
62      @Override
63      public WhileAction compileIt() {
64          return (
65              new WhileAction(
66                  predExpr.compile(),
67                  bodyExpr.compile()
68              )
69          );
70      }
71  
72      /**
73       * @see org.millscript.millscript.expr.Expr#resolve(org.millscript.millscript.vm.CompilerState)
74       */
75      @Override
76      public void resolve( final CompilerState state ) {
77          this.predExpr.resolve( state );
78          this.bodyExpr.resolve( state );
79      }
80  
81      /**
82       * @see org.millscript.millscript.expr.Expr#showComponents(int)
83       */
84      @Override
85      void showComponents( final int n ) {
86          this.predExpr.show( n );
87          this.bodyExpr.show( n );
88      }
89  
90  }