help/info/activate.html

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  18 <title>activate</title>
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  36 <hr>
  37 <h1>activate</h1>
  38 <hr align="left" width="75%">
  39 <p>The operation is used to activate a default context (i.e., an <a href="altstep.html"><b><font face="Courier New" size="4">altstep</font></b></a>). It returns a reference to the activated
  40 default.</p>
  41 <ul>
  42   <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
  43     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 â\80¦ statements. When no
  44   branch of the alt matches the received message, the previously activated default(s) are examined.</li>
  45   <li>The default reference can be used to <b><a href="deactivate.html"><font face="Courier New" size="4">deactivate</font></a></b> a given default.</li>
  46   <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
  47   variables to handle default references.</li>
  48   <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>
  49 </ul>
  50 <p>Related keywords:</p>
  51 <ul>
  52   <li><a href="alt.html"><b><font face="Courier New" color="#003258" size="4">alt</font></b></a></li>
  53   <li><a href="altstep.html"><b><font face="Courier New" color="#003258" size="4">alstep</font></b></a></li>
  54   <li><a href="deactivate.html"><b><font face="Courier New" color="#003258" size="4">deactivate</font></b></a></li>
  55   <li><a href="default.html"><b><font face="Courier New" color="#003258" size="4">default</font></b></a></li>
  56   <li><a href="null.html"><b><font face="Courier New" color="#003258" size="4">null</font></b></a></li>
  57 </ul>
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  62   <tr>
  63     <td width="100%">
  64     <h3 align="center"><font face="Courier New" color="#003258" size="5"><b>activate(</b></font><i>altstep_ref</i><font face="Courier New" color="#003258" size="5"><b>)</b></font></h3>
  65     </td>
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  67 </table>
  68 </center>
  69 </div>
  70 <ul>
  71   <li>
  72   <p><i>altstep_ref</i> is the&nbsp; reference to the altstep to be activated as default.
  73   </li>
  74 </ul>
  75 <hr align="left" width="50%">
  76 <p>Example 1:
  77 <p><font face="Courier New">var default vd_DefaultVar := null;<br>
  78 DefaultVar := activate(as_MyDefAltstep());<br>
  79 </font>
  80 <p>The variable DefaultVar will hold the reference to the altstep activated as default (as_MyDelAltstep).</p>
  81 <hr align="left" width="25%">
  82 <hr align="left" width="25%">
  83 <p><a HREF="BNF.html#activateop">BNF definition</a> of <font face="Courier New">activate</font></p>
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