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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.office.spreadsheet.formula.syntax;
22  
23  import org.millscript.millscript.expr.ConstantExpr;
24  import org.millscript.millscript.expr.Expr;
25  import org.millscript.millscript.syntax.BothfixSyntax;
26  import org.millscript.millscript.syntax.Parser;
27  import org.millscript.office.spreadsheet.formula.expr.AddExpr;
28  import org.millscript.office.spreadsheet.formula.expr.SubExpr;
29  
30  /**
31   * This class implements arithmetic syntax. In some ways this is a variation of
32   * {@link InfixSyntax}, as the arithmetic operator sits between it's operands.
33   *
34   * <p>
35   * <code>&lt;expr&gt; -- &lt;expr&gt;</code>
36   * </p>
37   *
38   * @see AddExpr
39   */
40  public final class SubSyntax extends BothfixSyntax {
41  
42      /**
43       * @see org.millscript.millscript.syntax.PostfixSyntaxInterface#postfix(java.lang.String, int, org.millscript.millscript.expr.Expr, org.millscript.millscript.syntax.Parser)
44       */
45      @Override
46      public Expr postfix( final String sym, final int prec, final Expr lhs, final Parser parser ) {
47          // Read the right hand side expression
48          Expr rhs = parser.readExprPrec( prec );
49          // Return a new arithmetic expression for the parsed syntax
50          return new SubExpr( lhs, rhs );
51      }
52  
53      /**
54       * @see org.millscript.millscript.syntax.PrefixSyntaxInterface#prefix(java.lang.String, org.millscript.millscript.syntax.Parser)
55       */
56      @Override
57      public Expr prefix( final String sym, final Parser parser ) {
58          // A minus prefix simply negates the operand
59          return new SubExpr(
60              new ConstantExpr( Integer.valueOf( 0 ) ),
61              parser.readExpr()
62          );
63      }
64  
65  }