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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.Expr;
24  import org.millscript.millscript.expr.NameExpr;
25  import org.millscript.millscript.expr.VarExpr;
26  
27  /**
28   * This class implements <code>var</code> syntax. This is used for declaring new
29   * variables. An instance of this class can be used to parse either variables or
30   * constants, by passing a flag on construction.
31   *
32   * <p>
33   * <code>var &lt;expr&gt; = &lt;expr&gt;</code>
34   * </p>
35   *
36   * <p>
37   * The left hand side expression must be a name, while the right hand side
38   * expression can be any expression that returns a single result.
39   * </p>
40   *
41   * @see VarExpr
42   */
43  public final class VarSyntax extends PrefixSyntax {
44  
45      /**
46       * Indicates if this variable is a constant.
47       */
48      private boolean isConst;
49  
50      /**
51       * Constructs a new <code>VarSyntax</code> for parsing variable syntax.
52       *
53       * @param   isconst indicates if this syntax parser is for parsing variables
54       *                  or constants
55       */
56      VarSyntax( final boolean isconst ) {
57          isConst = isconst;
58      }
59  
60      /**
61       * @see org.millscript.millscript.syntax.PrefixSyntaxInterface#prefix(java.lang.String, org.millscript.millscript.syntax.Parser)
62       */
63      @Override
64      public VarExpr prefix( final String sym, final Parser parser ) {
65          // Read the name for this variable
66          NameExpr name = parser.readName();
67          parser.mustRead( "=" );
68          // Read the value expression for this variable
69          Expr value = parser.readExpr();
70          return new VarExpr( isConst, name, value );
71      }
72  }