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.WhileExpr;
25
26 /**
27 * This class implements the <code>while</code> syntax. This syntax represents a
28 * simple loop construct.
29 *
30 * <p>
31 * <code>while <expr> do <expr> endwhile</code>
32 * </p>
33 *
34 * <p>
35 * The while expression is evaluated on each pass of the loop, it must return a
36 * single, boolean, result. If this expression evaluates to <code>true</code>,
37 * the body expression will be evaluated, and the loop repeated. If the while
38 * expression is <code>false</code> the loop terminates.
39 * </p>
40 *
41 * @see WhileExpr
42 */
43 public final class WhileSyntax extends PrefixSyntax {
44
45 /**
46 * @see org.millscript.millscript.syntax.PrefixSyntaxInterface#prefix(java.lang.String, org.millscript.millscript.syntax.Parser)
47 */
48 @Override
49 public WhileExpr prefix( final String sym, final Parser parser ) {
50 // Read the while loop condition expression
51 Expr predExpr = parser.readExprTo( "do" );
52 // Read the body block
53 Expr bodyExpr = parser.readBlockTo( "endwhile" );
54 // Return a new while expression for the parsed syntax
55 return new WhileExpr( predExpr, bodyExpr );
56 }
57 }