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.Action;
24 import org.millscript.millscript.action.BlockAction;
25 import org.millscript.millscript.vm.CompilerState;
26
27 import java.util.Stack;
28
29 /**
30 * This class implements a block expression. A block is a simple wrapper for
31 * its body expression, except that it introduces a new scope to the compiler.
32 *
33 * @see BlockAction
34 */
35 public final class Block extends Expr< Action > {
36
37 /**
38 * The body expression for this block.
39 */
40 private final Expr< ? > body;
41
42 /**
43 * Boolean indicating if this block is used.
44 */
45 private boolean isUsed = false;
46
47 /**
48 * Creates a new block expression with the specified body.
49 *
50 * @param e the body expression for this block
51 */
52 public Block( final Expr< ? > e ) {
53 body = e;
54 }
55
56 /**
57 * @see org.millscript.millscript.expr.Expr#compileIt()
58 */
59 @Override
60 public Action compileIt() {
61 // Compile the body
62 Action alpha = body.compile();
63 // Check if this block is used, if it is return a new block action,
64 // otherwise just return the compiled body.
65 return isUsed ? new BlockAction( alpha ) : alpha;
66 }
67
68 /**
69 * @see org.millscript.millscript.expr.Expr#resolve(org.millscript.millscript.vm.CompilerState)
70 */
71 @Override
72 public void resolve( final CompilerState state ) {
73 // Introduces a new scope prior to renaming the body of this block.
74 // After renaming the body, the scope is reset to it's prior state.
75 // This allows use to have variables of the same name within nested
76 // blocks of code, but ensure that the correct ones are shared.
77 Stack< Expr > scopes = state.getScopes();
78 int n = scopes.size();
79 scopes.push( this );
80 body.resolve( state );
81 scopes.setSize( n );
82 }
83
84 /**
85 * Marks this block as used.
86 */
87 public void setIsUsed() {
88 isUsed = true;
89 }
90
91 /**
92 * @see org.millscript.millscript.expr.Expr#showComponents(int)
93 */
94 @Override
95 void showComponents( final int n ) {
96 this.body.show( n );
97 }
98
99 }