2 Copyright (c) 2000-2015 Ericsson Telecom AB
4 All rights reserved. This program and the accompanying materials
5 are made available under the terms of the Eclipse Public License v1.0
6 which accompanies this distribution, and is available at
7 http://www.eclipse.org/legal/epl-v10.html
11 <meta http-equiv=
"Content-Type" content=
"text/html; charset=utf-8">
12 <meta http-equiv=
"Content-Language" content=
"en-us">
13 <title>default
</title>
15 <body bgcolor=
"#DAD3C5" vlink=
"#0094D2" link=
"#003258">
16 <table align=
"left" border=
"0" cellspacing=
"0" cellpadding=
"0" valign=top
>
18 <td width=
105 height=
40><a href=
"https://projects.eclipse.org/projects/tools.titan"><img src=
"../images/titan_transparent.gif" border=
0 width=
105 height=
40 align=
"left" alt=
"Titan"></a></td>
21 <table border=
"0" align=
"right" cellpadding=
"0" cellspacing=
"0">
23 <td><a href=
"../titan_main.html" alt=
"contents"><img border=
"0" src=
"../images/ao.jpg" width=
"53" height=
"40"></a></td>
24 <td><a href=
"../titan_index.html" alt=
"index"><img border=
"0" src=
"../images/up.jpg" width=
"53" height=
"40"></a></td>
25 <td><a href=
"decvalue.html" alt=
"previous"><img border=
"0" src=
"../images/left.jpg" width=
"53" height=
"40"></a></td>
26 <td><a href=
"derefers.html" alt=
"next"><img border=
"0" src=
"../images/right.jpg" width=
"53" height=
"40"></a></td>
33 <hr align=
"left" width=
"75%">
34 <p>The default type is an implementation dependent special type which stores the default reference.
</p>
36 <li>Default context is a set of branches (cf.
<a href=
"altstep.html"><b><font face=
"Courier New" size=
"4">altstep
</font></b></a>) that is implicitly appended at the end of all
<a
37 href=
"alt.html"><b><font size=
"4" face=
"Courier New">alt
</font></b></a> statements (except if the alt has an else branch) and after all stand-alone receive/timeout/done … statements. When no
38 branch of the alt matches the received message, the previously activated default(s) are examined.
</li>
39 <li>A default reference is the result of an
<b><a href=
"activate.html"><font face=
"Courier New" size=
"4">activate
</font></a></b> operation.
</li>
40 <li>The reference can be used to
<b><a href=
"deactivate.html"><font face=
"Courier New" size=
"4">deactivate
</font></a></b> a given default.
</li>
41 <li>The special value
<b><a href=
"null.html"><font face=
"Courier New" size=
"4">null
</font></a></b> is available to indicate an undefined default reference, e.g. for the initialization of
42 variables to handle default references.
</li>
43 <li>It is possible to have several defaults activated at same time and deactivate them one by one. The last activated default will be placed first in the list of the activated defaults.
</li>
45 <p>Related keywords:
</p>
47 <li><a href=
"activate.html"><b><font face=
"Courier New" color=
"#003258" size=
"4">activate
</font></b></a></li>
48 <li><a href=
"alt.html"><b><font face=
"Courier New" color=
"#003258" size=
"4">alt
</font></b></a></li>
49 <li><a href=
"altstep.html"><b><font face=
"Courier New" color=
"#003258" size=
"4">alstep
</font></b></a></li>
50 <li><a href=
"deactivate.html"><b><font face=
"Courier New" color=
"#003258" size=
"4">deactivate
</font></b></a></li>
51 <li><a href=
"null.html"><b><font face=
"Courier New" color=
"#003258" size=
"4">null
</font></b></a></li>
53 <hr align=
"left" width=
"50%">
56 <table border=
"0" width=
"90%" bgcolor=
"#FFB599" cellpadding=
"4">
59 <h3 align=
"center"><font face=
"Courier New" color=
"#003258" size=
"5"><b>default
</b></font></h3>
65 <hr align=
"left" width=
"50%">
67 <p><font face=
"Courier New">var default vd_MyDefaultVar := null;
<br>
69 <p>A variable called vd_MyDefaultVar is declared and initialized with the null value.
</p>
70 <hr align=
"left" width=
"25%">
71 <hr align=
"left" width=
"25%">
72 <p><a HREF=
"BNF.html#defaultkeyword">BNF definition
</a> of
<font face=
"Courier New">default
</font></p>