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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.syntax;
22  
23  import org.millscript.millscript.expr.AndAbsentExpr;
24  import org.millscript.millscript.expr.Expr;
25  
26  /**
27   * This class implements <code>&amp;&amp;</code> syntax.
28   *
29   * <p>
30   * <code>&lt;expr&gt; &amp;&amp; &lt;expr&gt;</code>
31   * </p>
32   *
33   * <p>
34   * The expression on the right hand side will only be executed if the left hand
35   * side returns not <code>null</code>, e.g. it is equivalent to writing:
36   * <code>if x /== absent then y else absent endif</code>
37   * </p>
38   *
39   * @see AndAbsentExpr
40   */
41  public final class AndAbsentSyntax extends SimplePostfixSyntax {
42  
43      /**
44       * Returns an {@link AndAbsentExpr} for the parsed syntax. The left and
45       * right hand side expressions are parsed generically in {@link
46       * SimplePostfixSyntax}
47       *
48       * @param   lhs expression returning any value
49       * @param   rhs expression to be executed if the <code>lhs</code> is not
50       *              <code>null</code>
51       * @return  an {@link AndAbsentExpr} for parsed expression
52       */
53      @Override
54      public AndAbsentExpr simple( final Expr lhs, final Expr rhs ) {
55          return new AndAbsentExpr( lhs, rhs );
56      }
57  
58  }